Cellphone drama

Hey guys first time posting. So me and my boyfriend have been together for almost a year now and I think yesterday we might have broken up. We spend the morning at a springs with some friends and I saw that he had gotten a message. (Snapchat) He has his phone set up in a way that it won’t show whose the message from or what it says. But later on the day I saw it was from a girl and that he replied. Ok no big deal, but when we are driving back home I’m one his phone and that whole chat thread is gone. Now I don’t understand why he feels he would have to delete that whole chat unless he feels he has to hide something. This is not the first incident of shady actions with his phone, and what frustrates me the most is that when I confront him about it he denies it or acts stupid. I’m 24, I’m honestly done playing around and I’m looking for someone serious and someone I can trust. But I see it very hard to be able to trust someone who can’t even man up and take responsibility. What do you guys think?