What Happens to Mortgages Held at Banks?

If a big bank such as Wells Fargo goes away, what happens to mortgages held at the bank? The FDIC or an entity was created back when the savings that there were a lot of savings and loans going down. It's not a huge risk of the person who has the mortgage because it's going to continue to be surfaced. And remember that you borrowed the money from them rather than the other way around.