Why was Yoren presumed dead, rather than a deserter?

[Selere]

Quote

Even Dareon would be happier. He had always claimed to be innocent of the rape that sent him to the Wall, insisting that he belonged at some lord's court, singing for his supper. Now he would have that chance. Jon had named him a recruiter, to take the place of a man named Yoren, who had vanished and was presumed dead. His task would be to travel the Seven Kingdoms, singing of the valor of the Night's Watch, and from time to time returning to the Wall with new recruits.

-Samwell II, AFFC.

The Night's Watch isn't unfamiliar with deserters. As the vows of their members are for life, those who try to run away are executed. We know what happens with Yoren in ACOK, from Arya's point of view, but it wouldn't be unexpected that the NW would have no idea what happened to him after they send him to King's Landing to fetch recruits and was never seen again. From their perspective, wouldn't it make more sense to assume he took that opportunity to change names, get a haircut and take a ship to Pentos to live a new life under a new identity? 

[TheMiddleHero]

14 minutes ago, Selere said:

-Samwell II, AFFC.

The Night's Watch isn't unfamiliar with deserters. As the vows of their members are for life, those who try to run away are executed. We know what happens with Yoren in ACOK, from Arya's point of view, but it wouldn't be unexpected that the NW would have no idea what happened to him after they send him to King's Landing to fetch recruits and was never seen again. From their perspective, wouldn't it make more sense to assume he took that opportunity to change names, get a haircut and take a ship to Pentos to live a new life under a new identity? 

I would guess that the reason is that Yoren has been a devout Nights Watchmen for years and has successfully brought many loads of recruits in this manner for years, and would not be suspected of deserting. So in essence his inability to arrive with the recruits would be seen as extremely unusual than the expected outcome. I doubt they would send someone south to recruit that had dubious intentions of returning.

[Aurane]

Yoren has been a recruiter for a while. He likely gained a level of trust and respect throughout the years to earn himself a recruiter position.  He was also in the middle of the war of 5 kings when he died. (Even if someone knew that he successfully abandoned the Night's Watch, it's best not to tell Castle Black about it)

[Seams]

This is actually a really good question.

Why do they put tons of effort and resources into finding Benjen - even putting lives on the line - but quickly presume the Yoren is dead?

They probably do have more information coming from the Riverlands, where Yoren's group was attacked by Amory Lorch's group, of course. They know that Lorch and Clegane have been wreaking havoc there, along the with "wolves" from the North. They probably had word from King's Landing when Yoren departed or they followed up and gathered information about his departure date and how many in his wagon train after he went missing. Maybe they obtained updates from people who had seen him and his recruits along the way. The Night's Watch might have sent people to inquire at inns along the route, to figure out when Yoren was last seen or to collect reports about any escaped recruits who had been traveling with him.

All speculative, of course.

I had an inkling some time ago that Yoren plays a role in Arya's arc that is similar to the role played by Qhorin in Jon's arc. In Sansa's arc, the same role is filled by Arys Oakheart, of all people. He is one of the guards who beats Sansa when Joffrey orders it (Yoren spanks Arya to punish her for attacking Hot Pie) and he escorts her to Joffrey's name day tourney, where she meets Ser Dontos. Arys doesn't die in Sansa's arc (as Qhorin and Yoren apparently die in Jon and Arya's arcs) but, we find out later, he does die in Arianne's arc. (Which may invite us to compare Arianne and Sansa at the same time we are comparing Yoren, Qhorin and Ser Arys. Or maybe the comparison is between Myrcella and Sansa?)

[Bael's Bastard]

It's easier to presume him dead than to presume him a deserter. It's not as though he turned up as a verifiable deserter like Gared did. He went missing during a massive war, and they have no evidence he deserted.

Aside from that, perhaps Yoren is given the benefit of the doubt because he has spent nearly thirty years traveling the Seven Kingdoms to find new recruits and bring them to the Wall.

"Been bringing men to the Wall for close on thirty years." Froth shone on Yoren's lips, like bubbles of blood. "All that time, I only lost three. Old man died of a fever, city boy got snakebit taking a shit, and one fool tried to kill me in my sleep and got a red smile for his trouble." He drew the dirk across his throat, to show her. "Three in thirty years." He spat out the old sourleaf. "A ship now, might have been wiser. No chance o' finding more men on the way, but still . . . clever man, he'd go by ship, but me . . . thirty years I been taking this kingsroad." He sheathed his dirk. "Go to sleep, boy. Hear me?"

ACOK: Arya III

Even in the case of Gared, Lord Commander Mormont notes that he never would have believed that he had deserted had Ned not sent his head from Winterfell.

The Lord Commander took no notice of the irritating bird. "Gared was near as old as I am and longer on the Wall," he went on, "yet it would seem he forswore himself and fled. I should never have believed it, not of him, but Lord Eddard sent me his head from Winterfell. Of Royce, there is no word. One deserter and two men lost, and now Ben Stark too has gone missing." He sighed deeply. "Who am I to send searching after him? In two years I will be seventy. Too old and too weary for the burden I bear, yet if I set it down, who will pick it up? Alliser Thorne? Bowen Marsh? I would have to be as blind as Maester Aemon not to see what they are. The Night's Watch has become an army of sullen boys and tired old men. Apart from the men at my table tonight, I have perhaps twenty who can read, and even fewer who can think, or plan, or lead. Once the Watch spent its summers building, and each Lord Commander raised the Wall higher than he found it. Now it is all we can do to stay alive."

AGOT: Tyrion III