So I was rewatching the new season 6 trailer (again) and something occurred to me.. During the part where Lydia crying against the wall while she and Stiles are back to back, you can clearly see her holding something in her hand that looks like paper. I'm thinking that maybe that piece of paper could be the letter that Aiden finds in Stiles' room in 3x18 that said "For Lydia." I know that at this point Stiles has already been erased, but maybe somehow Lydia still finds it? What do you think?
I’ve seen some people bring this up as a point before, but my favorite theory is one that was first told to me by @stilesbanshee. I will summarize it for you! (Also I know @hollandroden mentioned it in her big trailer recap analysis. And probably @deathcabjenny somewhere because she’s got a good eye as well).
Lydia goes to the Stilinski house a few days after Stiles is taken and tries to convince the Sheriff that something is missing, specifically something that should be at his house. She ends up going upstairs, insisting that there’s supposed to be another bedroom (think in 3b where Lydia is sure Stiles is supposed to be in the Eichen House basement). Frustrated when there isn’t one, she attempts to peel off the wallpaper to find the room but starts crying when she isn’t successful.
She probably manages to tear off a chunk, which is what we see in her hand. Kay (and others) have pointed out that what Lydia is holding looks too hefty to be a piece of paper, which is what we know the “For Lydia” note was written on. It’s also slightly yellowish, kind of like the wallpaper! Kay also mentioned that Lydia could be feeling especially devastated because some more memories of Stiles (Episode 2x11, anybody?) come rushing back because she’s in his house, in front of his room.
And then (now for the part of the theory that I personally noticed after the first trailer dropped), later, the Sheriff will come up and see what Lydia’s done and peel more of the wallpaper away revealing…
Stiles’ empty room!
For me, this seems a lot more logical than Lydia somehow finding that note, although that would make for an adorably heart-rending scene.