I lost 4 grams of coke once..
We were out clubbing, and went to a place that was notorious for very throrough searches, so I hid it down my knickers. (this was before I did coke myself and was looking after it for my b/f.
Anyway, a few minutes after we got in there, I went to the toilet...completely forgot it was there. (I was slightly intoxicated %))
About 20 mins later he asked me for it, so I was like yeah sure, and then I just had this horrible feeling come over me.
Went back to the toilet to get it out, and it was gone 8) Sure enough, I had dropped it and flushed it and hadn't even fucking realised....
So b/f spent the best part of the night trying to persuade our guy to drive back into town and bring more (which was covered in cops as there had been a stabbing the night before)
He eventually did, and as I recall it was a good night.
It wasn't so much of a big deal to me, because at that time, the only narcotic i'd ever had was weed....but i'd be pissed if it happened now
Oh and we also lost a big chunk of hash down the mother in laws sofa, we always get out hands down the sides of it if we visit for christmas.....

*no joy as of yet*