It is most likely a revenge or prank. It is usually on a woman who carries a large or oversized purse. It could also be in any type of bag carried by a male or female.
Originated from the movie Borat (who is Eurasian), where he shits in a bag and presents it to a group of people.
Steve: Damm, that sucks man.
Joe: It's ok. She looked better with the beer goggles on anyhow. Before I left I dropped a Eurasian Traveler in her purse. Probably won't be hearing from her again.
Steve: Ouch, she'll probably reach in there for her wallet and get a nasty surprise.
Joe: Definitely have to wash your hands after you meet the Eurasian Traveler.