Looking through my SO phone

My hubby left his phone in our bedroom. I went in there to get my tablet. He then put our daughter down, and was trying to sneak up on me(tip toeing). He thought I was looking through his phone. He didn't admit to it, but I knew that's what he thought. 
We have a spare bed in our daughter's nursery, she sleeps with me. He sleeps on the spare bed(he has to sleep on a firm bed because of his back and his work schedule) but he hates when I step two feet into her room. He'll run in there and try to get me out. WTF is in there? Should I be suspicious?
P. S. He's been caught trying to hook up with girls on his phone three years ago, and naked pictures of his "friend"  on there. I forgave him and don't even think about it, until he acts like this.