If it's foreclosed then you are no longer the owner and not responsible for any taxes from the day of auction date. You must have received the notice of sale and the sale date in that letter. Keep that letter with you for your future reference, you may need it for any proof.

Consult with an attorney also to check whether your house is actually sold in auction to any third party or the lender is the new owner. Attorney has the power to check further or check with the lender who is the new owner or what happened at auction.

I agree, consult a real estate attorney. Some banks are holding off recording to try to work it out with the owner after foreclosure.

You need to consult with a real estate attorney.

If a property is sold at foreclosure, then the deeded is recorded. It may vary by jurisdiction, but typically occurs within 1-3 days after purchase.

The "prior owner" is the lender. Ownership moved from "original owner" who was foreclosed upon to the lender who took title to the property, and then from the lender to the new purchaser.

Your lender is under no obligation to give you any information about who it sold the house to. That transaction was between the lender and the home buyer. You're out of the picture. Check with your city or county (as apparently you've been doing) to determine--from the recorded deed when it's filed--who the new owner is. But I'm not sure why--other than for curiosity's sake--you care or why it matters.