In ye oldene dayz we would use the same approach as with a leader retriever; but we would take a fresh roll of film, wet the the leader on both sides by sticking it in the mouth, then push it in. Turning the problem film tight in the cartridge to make contact with the wet leader, waiting a coupla seconds, then pulling out. You would be amazed how often it would work, with most films, and with most sources of spit.
Careful John: In this day and age you'll be getting a visit from the DEC, EPA, FDA - and probably the Anti-Terrorist Squad!!! (Do you know how to assume the position?)