For practical purposes a BK is treated almost the same as a foreclosure. Not quite sure why that is worrying you, but if the mortgage was not listed in the BK that is easy to prove, just send a letter and copies of your BK papers simultaneously to all three credit bureaus. Personally, I would not do that, but that is how to get it straightened out. You will never get the lender to fix it by going direct to them.
Be sure to read the info on my blog about credit scores, see the link below