I left a Polaroid pic in her nightstand.
This is the days before d.i.c.k. pics. I was at at party in the 90s with my wife. The couple had a large house and it was filled, wall to wall, with people. The man was a successful car dealership owner/partner and the wife was a hottie, blond, big tits, and really flirty. She had made a drunken comment about her husband not pleasing her in bed and everyone laughed. She said, "I wouldn't mind another dick every now and then."
I was later looking for another bathroom so I went upstairs since the two downstairs baths were occupied as was the one upstairs in the main hallway. I found the master bedroom and headed toward the bathroom there. On my way, I saw a Polaroid camera on the dresser. I went into the bathroom, got myself hard, and took a photo of it, leaving my clothes out of the pic along with any other identifying features. I placed it in her underwear drawer.
About a week later, my wife came home after lunch with this woman and said, "Carolyn found a picture of an erect p.e.n.i.s. in her underwear drawer. She showed it to me....know anything about it?" Of course, I denied it. My wife said that Carolyn wasn't particularly offended but found it very amusing and flattering. My wife had a smirk on her face so I think she knew what really happened and recognized the suspect.