We've been very, very lucky with DS1. He's never flushed or otherwise destroyed anything.
We haven't really allowed him access to the bathroom though. He's just now potty training at 3, and he's too short to go #2 on the toilet so he's using the little potty pretty much exclusively.
Robbyn, SAHM to Silas, 4/3/09 and Griffin, 3/23/12