Two summers ago, my wife and I attended a wedding that took place over a long weekend at a lake side resort. There were a number of little cabins on the lake, and my wife and I grabbed a nice easterly facing place.
The night before the wedding was a beach side BBQ party, and we enjoyed ourselves very much with dancing, drinking, and a little quickie under the deck of the closest cabin.
Throughout the night, we talked about dragging our mattress on the deck to watch the sunrise in the morning.
Fast forward to the next morning, and we both woke-up very confused. We were on an air-mattress (we had no clue where that came from) on the deck. When I sat up to look around, I realized we were sleeping under some sleeping bags (again, not ours), and that I was naked. Upon looking under the sleeping bag, I could see wife was naked as well, and there was an obvious cum stain on the sheet. A smell of my fingers confirmed it: we had sex last night.