My favorite is when I dropped it, the teacher asked if I had a quarter out, and I put it in the Goshman pinch to show my hands empty, then she resumed writing on the board, and I resumed coin rolling
Same thing happened to me a couple of weeks ago. I was practising the 1 card pirroette (the little flourish were the single cards spins around you finger), The rest of the deck was in my pocket. The teacher said "give me the card" I quickly put it in backpalm and said "What card?" The teacher had the funniest look on his face. Kodak moment!
As for the coin roll. I havent ever been bothered timing myself. I just do it every now and then when im doing coin magic and someone says - ""Hey, can you do that thing with the coin that johnny depp does in POC?"