Dear "The house I'm renting":
Look up the ownership of the real property on your county's property appraiser website.
The "Owner of Record" is the true owner.
It sometimes takes a few weeks after the sale for the property appraiser's office to make the change.
You can also look up the foreclosure case online to see who the successful bidder was at the foreclosure sale.
You should pay rent to the true owner. If you are unsure of who that is, keep the money aside and be ready to pay it upon demand.
You can write a certified letter to the former owner demanding your security deposit back since your contract with him is now over. If he doesn't return it, you can sue him unless he can prove that he sent the money to the new owner.
Yes, you can still accept a "cash for keys" offer if the bank offers it to you.
Banks don't always tell the truth, so check out the real story at the property appraiser's office website. Good luck! If you are unsure, see a local lawyer.