(SPOILERS!!)
During Rune's route, Arvo, Rune, Mikko, Travis, Lake, and Torulf will play the game Never Have I Ever to pass the time. When it's your turn and you choose the 'Never have I ever stolen anything' option, Travis will be the only one to admit that he has stolen something before. He did it because, and I quote: "I had a friend who wanted to get back with their old friend, and I felt they needed a small nudge. So to help him I took something from that person for a while... but as soon as I noticed it wasn't working I returned it."
Obviously, the 'friend' Travis is referring to is Mikko, and who else is Mikko's old friend but Arvo? And the item Travis stole is without a doubt Arvo's room key. I never expected it lol