For me, the right thing would be to return 12k and keep the 2k for the trouble and possible loss of sale to someone else.
Last month i had a renter sign a lease to rent my old house. I took it off the market for 30 days and then 3 days before he was supposed to move in, he sent my real estate agent a letter saying that his family plans have changed and he was going to stay in D.C. and not move afterall.
Legally, i could take him to court for the $17k he owes me in rent. Instead i kept his security deposit for the 30 days that i had the house off the market. It has not rented back out yet, but I sleep well at night.
In my opinion i have a better case than LDD, but i know the difference between right and wrong. No matter what, LDD keeping 12k of someones money without providing anything in return is pure thievery.