Surfer of Saragar

If you're right, why he thought specifically Theon? It could be any Greyjoy or any Iron born captain. It is strange. That is a good point. But the north does not have a true navy since Brandon the Burner. And what he saw was iron born sails with the squid symbol. And he knows that Ned is dead, he leaved after that.

This is, in some way, a confirmation of the R+L=J theory. Why would Ser Barristan think that Theon Greyjoy would send help to Daenerys? Unless he know that R+L=J is true and thinks that the Starks would eventually discover this and send help to the last living Targaryen that didn’t take the black.