A word for someone who pretends to be interested in a home for sale

I need a word for a third person who goes into a home for sale to increase the price by pretending to be interested in a home for sale.

A number of online sources refer to this individual as a "phantom buyer." See, for example, Larry Lloyd, "Buying a Home - the Phantom Offer" (July 8, 2008), posted on activerain.com:

With a phantom buyer the seller will actually create an imaginary person with good credit. They will create a fake contract that includes a higher price than what you have been offering. However since you are not allowed to actually see and read the competing offers you cannot really tell if the offer is legitimate.

And Colin Barrow, Buying a Property in Spain For Dummies (2007):

Make sure you're bidding against a real person: Agents have been known to be less than honest, creating a phantom buyer by saying someone else is in the running. Ask as many questions as you can: Who is the other bidder? Does she have somewhere to sell first? When does she want to move in? If the agent doesn't know or is evasive, there's probably no one else in the running.

I should add as a cautionary note here that "phantom buyer" is sometimes applied to other deceptive participants in property sales as well as to imaginary would-be buyers drummed up by the seller of the property to create artificial competition for the property. In one scenario, the "phantom buyer" is actually a front for a real estate company that is hoping to stake a claim to property that it has yet to find a buyer for; in another, the "phantom buyer" is simply a person who likes to look at property and feign interest in buying it but ultimately has no intention of submitting a serious offer.