You haven't said which bank it was, but I'm aware of a number of investigations into areas like this, a few leading to prosecutions. But it's a long time since I saw one. The banks are the victim here, so I can't see any reason they'd want to brush it under the carpet?Perhaps the bank was afraid to open a can of worms, and possibly unearth other similar cases?
It's unusual that this is all coming to light years after the property was repossessed. It should have been investigated / challenged at that time. In fact, it's at that stage a number of 'irregularaties' came to light and led to banks investigating specific brokers (and staff in one case I'm aware of).