>>11368833You have it backwards, yku should especially consider faster piss streams. The larger forces shoot aerosol droplets that contain other solid phase particles into the air. There is no reason to assume you never get toilet water splashing back in the direction of your urine stream.
It's literally guaranteed to happen at larger initial piss velocities. The real question is finding the distribution at "normal" piss rates, then you can compute the probability of being hit by the toilet water.