Velvetee, I think it boils down to one thing - do you trust him?
Only you yourself know whether he is the faithful type, or whether he would cheat on you. If I had found such a paper in my hubby's pocket, I would instantly pull his leg about it, as I am so confident he would never cheat on me.
There could be a simple explanation for the blank piece of paper - I'd just ask him outright. And to be honest, even if he went to one of those places - surely he'd only be ogling a few scantily clad ladies - not really cheating, is it?