I like Caravaggio but I didn't even know there was a missing one. Thanks.
The missing Caravaggio was his "The Taking of Christ" (i.e. JC being arrested after the Last Supper), which had been lost for two centuries, known only through contemporary copies and which turned up in 1992 on the wall of a house owned by the Jesuit order in Dublin.
There's an interesting book out on the subject.