Boyfriend’s Tinder

So my boyfriend and I have been together for 6 months. I am completely in love with him and we plan to move in together in a few months. His Apple watch ended up in my purse and I happened to look at the messages on there. He got a code to use to log into Tinder... he claimed he had no idea what it was and it wasn’t on his phone. He has given me no reason not to trust him. He says I am his world and he wants to marry me one day. But I’m struggling with how he has no idea where it came from and just doesn’t know. That doesn’t make sense to me. He got the code the day I left for spring break. I was gone for 11 days. I don’t know how to think or feel. Does anyone have any thoughts?