Yep, that is what just happened to me. Here is some advice on what to do: wikihow.com/Dry-Out-a-Wet-iPhone. Luckily, the toilet had already been flushed and the phone was too big to go down the hole. Still… remind me to spray it with Lysol when I get home!
Speaking of iPhones, if you've been locked out of yours (or your daughter's, as I was), this might help.