Should I open the message???

My husband works in a club. He was finishing at 1am. He was there with mates after having a drink and that's cool it opens until the early hours. However, he came home at 5am.
This morning he is in bed and his phone is at the side of him with a message flashed up from a girl we both know that says "yes, I'm looking at it now. Sorry when do you need it"
So two things - they have either gone back to hers (and quite possibly a few of them she lives on her own and has parties sometimes), or she's taken something of his by mistake and has it. I think I know what it is and it's not a big deal. 
So now I'm torn. Do I wait for him to get up and tell me about the night or do I read this message in case it is incriminating before he has a chance to delete it??
Thanks in advance!
Paranoid wife