(Warning: Wall of Text)
Oh dang, played that specific scene multiple times and never really connected those two events lmao.
Although I have a bit of a problem with this theory. I don't think there has been any time where Travis was alone with us in order for him to steal or return the key into our bag?
(I'm gonna be using Rune's route for easier explanation) Arvo finds the key while still being inside of Rune's room so if Travis were to return the key, it has to have happened the day prior. And if I recall correctly, every decision for "hang outs" has a decision where Travis isn't involved so that makes it hard for him to slip it back in the bag. There's also the matter of stealing the key in the first place which has the same issue and also, if I recall correctly, Arvo always has his bag on him so it's practically impossible for Travis to get it unnoticed. Also, there's the fact that Travis only just met Mikko so it would be very weird for Travis to risk his reputation by stealing Arvo's key. These are just my thoughts lmao
But then again, Travis' story matches up real well with Mikko and Arvo so that theory still has alot of credit.
(I didn't realize how big of a wall of text this is until I finished it lmao so sorry about that.)