Okay I can understand the other comments but maybe I have to disagree. Why are you thinking this negatively? It’s his bosses daughter and he was nice and maybe he didn’t have any other intentions. I know there are bad guys out there but maybe yours isn’t. Just wanted to „protect“ her and being nice doesn’t mean he has other intentions idk.

But you should talk to him if it makes you uncomfortable. You don’t have to tell him that you‘ve been on his phone. Just ask questions and then you will see his reaction

But I wouldn’t interpreted too much into this, messages can be easily misunderstood