What should I do?

Was going through my bfs Snapchat and saw he had recently been snap chatting this girl (I have no idea who it is) and their chats are set to delete after viewing. He had cleared the conversation from his feed but when you go to send a snap she’s at the top of his recent snaps.

Should I let it go or bring it up??? Idek what I would say. (He does has a history of cheating in the past)