What a funny story. At a horse show I was at this weekend they had an area of shavings for horses to pee on for those that wouldn't on the ground.
I'm positive my gelding hides objects from my grooming bucket. After I'm done putting everything away, I always find one item left out that I didn't see before!
My mare is a hose stepper too. She moves around during baths just a few steps and thinks about where to put her feet to stop the water.