Caught in the act or accidental?

Hey, girls I spent the weekend with my boyfriend outside of town. We went out and what not, so it was already getting extremely late. We take off into the car and as soon as my boyfriend turns on the car and and connects his phone the speakers started to play a dialing out sound from Snapchat. He then is like “what the heck” grabs his phone, I didn’t see anything on the radio screen I guess he had CarPlay taken off? But I look over his phone and seeing him exit out of his apps and the call out was from Snapchat and he opened it and exit it out really quick but when I glanced I saw a photo of some girl with her boobs super out but wearing a top. Definitely a seductive photo. I got so upset. He kept telling me sorry and it wasn’t what I thought it was. He doesn’t know how that happened. He wouldn’t do anything to make me look stupid, but then again he was all shaky. I don’t know if because I busted him or because I was upset at him he got all nervous and shaky. Has anyone had this weird experience? Or do you think he was already communicating with his girl? He was quick to tell me to go through his phone but I declined because I was so mad.