I haven't yet read through the entire thread so apologies in advance if someone else has said this already.
If you pause the episode at the 33:47 mark you can see the Qot playing with Sansa's hair-braid-thing and you can just detect a hint of metal in her fingers. Then if you look again at the 33:49-50 mark, you can see that the stone that's right next to her braid is missing. It's harder to tell since her dress is a much more similar color than her skin, so the stones that are against her skin stand out MUCH more. As far as I can tell, it looks like a missing stone to me. It's not something that an unsullied (I assume that's a term for those who watch the show but haven't read the books?) would catch, but knowing exactly what to look for really helped. It was quite subtlety done actually imo.