Wallet Fossil
An unused condom that has been tucked away in a wallet for so long that it's actually fused with the leather, and must be carbon dated to determine the era in which it was intended for use. A wallet fossil should not be discarded as it may be worth money on the collector's market, or at least holds value as nostalgia for the days you still held out some hope for pussy.
"The date had not gone well, and Laura felt an awesome wave of relief when their waiter finally appeared with the check. As Chad took out his Harley-Davidson wallet to pay, Laura noticed a scuffy ring-shaped extrusion on it that can only be produced by a long forgotten wallet fossil. Suddenly it all made sense to her."