this happened to me, too! except it was because the condom was too small
poor boy. i didnt freak out too much since i was on the pill, but that was certainly scary. he came out and realized it wasnt there and freaked. we searched the bed for a good 10 minutes until we both realized where it could be. its so not sexy having a guy poking around in there looking for a foreign object. just stay on the BC. gotta love that piece of mind.