Sheriff's sale of property in Iowa?

There was a sheriffs sale of a house today in Iowa.
There was a mortgage of $67,763 on the house by the mortgage company that did the foreclosure. That company only bid $15120 on the house. Does that mean that they would have forgave the rest of the loan if I had bid a dollar more than them. I understand that other leans would have still been active if there was any but since this is the company that did the forclosure would they not have had to bib the $67763 that they was owed. I think that is the way most of the sherriff's sales go. The mortgage company usually bids what they are owed. I'm just not understanding this one now.

Read more: Sheriff's sale of property in Iowa?