Is this suspicious or am I crazy?

My husband never lets me use his phone.... well tonight while he was sleeping I went through it. He does text a girl from work all the time but he deleted the messages and he’s sworn to me it’s just about work. I know her and I consider us friends. Well anyways I go through his notes (he types out things in notes sometimes when he’s mad and trying to figure the best way to word it) I find a message from A few months ago that’s says “it really bothered me that you thought I paid for dinner for something in return” Well seems weird so I start my digging. I go on my phone and I look up that date and the date before and BAM we went to dinner with this girl(who he swears is just a co worker and friend) and he payed. I’m going to confront him tomorrow