Have you ever been caught masturbating?

Spoilers: You can actually clog the drain with your semen. Have fun explaining that to your mother.

I have done one of these two things. Depending on how good your drain is, how old your house is, and how often you do it, it can take several years to clog.

Clean it yourself before anyone notices

OR (if you don't have a drain you can clean yourself)

Claim that it's soap that's stuck to the drain-hair

And no, I've never been caught. It's really not that hard so long as you lock whatever door separates you from anyone who could see.