Ok so I go away for no more then an hour and come back and there is wet spots on my couch that have no smell?

I have 3 cats 2 unfixed ones. And I went away for no more then an hour and I come back sit down and notice my is wet so I stand up and smell the spot thinking OK Ewww my cat pissed on the couch (Never done it before) But it dosent smell like anything. I meen it literaly has NO smell at all. I was kinda wondering if because there in heat if they like.... licked themself to orgasum kinda thing. I know it sounds grose but I cant think of anything else it could be.