Wearing a condom whilst dry humping? (I assume that's what dry sex is? I don't know... XD)
Anyway, condoms are 'wet' because they are lubricated. Could the dampness have come from that?
I would say it's very unlikely seeing as he had a condom on, you were wearing underwear and he didn't actually go inside you... But if you really are worried then just do a test to ease your mind.