I freaked out. Then it freaked out, and, as it couldn't make it over the lip of the toilet, it thrashed about and swam back into the pipe. I could still see its tail so I flushed. 30 minutes later I had calmed down and cautiously returned to the scene, broom in hand. Sure enough, it had returned and it and I went through the same sequence of panic, with multiple flushes this time. Just in case, I threw a piece of cardboard in as a ramp. As much as I'd rather not have it running around my bathroom, there was no way I was going to ever use the toilet again if I thought it could swim up at any moment. I haven't seen it in months and, as there were no webbed footprints on the ramp when I returned, I assume it's still frolicking about down there somewhere, scaring everyone it encounters.