I feel like I should look through my best friend's phone.
Why do you want to look through your best friend's phone?
I want to see if he knows a girl I'm dating.
Can't you just ask if he knows her? I'm sure he wouldn't want you invading his privacy by going through his phone. If he finds out he'll be furious.
I don't care. He doesn't need privacy on his phone since he shows my all his pictures on the app. I'll do it when he's asleep.
It doesn't matter if you don't care, but how would you feel if your personal things were looked at by your friend? It would probably hurt, wouldn't it?