They rekeyed the whole house? If the home is listed and still in redemption, it's law in our state the bank can only rekey a side or entrance.
What do they do then if it is a second or higher story condo unit with only a front entrance?
I feel the OPs pain, as sometimes these properties are rekeyed without anyone's knowledge. You go out there and wham, you can't get in. My sucess rate is about 80% thereafter as I have about a dozen different Kwick Set/bank keys. If you know the lender, then sometimes you can figure out the combo for the lockbox. (ie Suntrust Bank uses the same combination for all their properties)
P.S. If the lockbox has a bank/AM key I don't already have, I make it SOP to "borrow" the key for a 1/2 hour or so and get a copy made. Chances are I may be able to use it again on a different property. Kwickset keys will actually have their five digit number on the back as a reference.