Not been caught to my knowledge (except by an SO, who joined in the fun), but I do have a terrible, soul-crushing, cold-sweats jizz story.
It was soon after I’d started - aged 14 or so - and as I was washing in the bath (we didn’t have a shower at that time), I started to mess about with myself, and before I knew it I was nearing completion. I had never seen what happened to spunk in water, and I sure as hell wasn’t about to find out while I was still sitting in it. I was too far from the toilet roll to get any, and the moment was at hand, so I just grabbed the nearest receptacle, which was one of those little disposable paper cups you use to rinse when you’re brushing your teeth.
Having dealt with that, and washed myself off, I then got dressed and went out to meet some friends in a neighbouring town. About 30 minutes after arriving, I suddenly got a cold sweat down my spine: I’d left the cup of jizz on the side of the bath.
I made my excuses to my buddies, jumped on my bike and hared it back home - to find the bathroom door locked. “Who’s in there?” I asked, and my dad answered “Me”, and I heard the sound of sploshing.
My dad, in the bath, with a cup of my fresh jizz, by his head.
Oh shit oh shit oh shit. The shame. I paced the house and blushed and sweated downstairs, until eventually heard him leave the bathroom, and I ran and retrieved it, wrapped it in tissue, put it in a plastic bag, left the house, and buried it in the woods.
No idea whether or not he looked in the cup - it would have been right by his ear - or, if he did look in it, whether or not he knew what it was. I’m just glad he didn’t think it was shampoo…