Mysterious Urinal

No, there's no photo. Sorry.

So, at work, there's a urinal. It's an auto-flush deal. We're all familiar with the auto-flush, yes? A little motion detector senses when you're there, and when you leave, the toilet flushes.

Alright.

Well, this urinal seems pretty normal. Except. Except.

Whenever I go into the bathroom, there's pee in it.

Gross? Sure.

But once you get past that...it dawns on you that it's also impossible.

The urinal is in a little corridor formed by bathroom walls. You can't sneak up on it (nor can I fathom why youd want to).

It NEVER fails to flush after I leave.

So, who is leaving the mystery-pee? I have come up with two potential solutions:

1) A thirsty ghost. (He's invisible, so the sensor doesn't notice him)

2) A thirsty giant. (He's so tall that the auto-flush sensor shoots between his knees - thus failing to register him)

Anyway, it baffles me.