Caught my best friend sniffing my bike seat, do I say anything to him?

I'm in school and a few of my buds and I go on long bike rides every weekend. After one such ride, back at my house, in the detached garage, my best friend and I lounge after the ride.I go inside via the side house door to get drinks but come back through the back door after putting out the garbage, so my friend never heard me coming back out. I glance in the side window of the garage as I'm walking to where he is and think I see him bent over sniffing my bike seat. A stop dead in my tracks, back up, and look again.He's bent over with his nose to my seat for like a minute before straightening up, than bends back over to smell my seat some more.I quietly walk back to the side house door, open and close it loudly so he hears me, and make my way into the garage. My friend is now seated in one of the folding chairs we have set up in the garage as if nothing is going on.What do i do? Confront him or let it go, he's never come on to me or is gay from what i can tell....thoughts?