Deleting texts

If your man is deleting messenger conversations with a girl, would you assume he is cheating? They go way back and idc if they're friends. But they've been talking a lot, I saw her name on his phone when I peeked over his shoulder. I went to check and he deleted their conversation.

UPDATE: I've caught him on more-than-friend messages before. Now I go through his phone on the regular. He gets mad when he catches me doing it. After last time he put a lock on it. I got mad and he took it off. But he carries his phone with him everywhere. I am afraid to question it cuz it proves I went through his phone again. He tells me that me doing that proves I don't trust him. But it's hard when he has done stuff behind my back before.

I also noticed they're talking through texting too. I read the convo and there are definately messages missing.