Unfortunately, the ones who don't come back are those who sought care elsewhere and got better treatment or unfortunately some of them ended up in a body bag. We never find out about those patients and that is worse in places like the emergency department, where they get virtually no follow-up on any of their patients either.
But it is also bad in primary care and other places where there isn't a mechanism whereby the system ensures that you will get follow up on all the patients who don't come back. We developed this delusional belief that because we are seeing patients in follow-up who are doing well that we must be right most or all of the time.
The other thing that is the fool's gold here is that most of the time our diagnostic mistakes don't harm patients. So we probably have a huge rate of diagnostic error. If you just look at autopsy data where the studies are reasonably clear and crisp around this issue 5% of autopsies done in hospitals suggest a Class 1 diagnostic error.
That means those are patients who died but had their diagnosis been correct they 'coulda, shoulda, woulda' left the hospital alive instead of in a body bag. That seems like a relatively small number. Certainly you can say 95% were right and that sounds good. But there weren't 95% all right. There is another 20% Class 2 error rate where we made major or significant misdiagnoses.
Then you start getting into other misdiagnoses that get further away from harm the rates get up into the 50% plus range. We are probably making diagnostic errors all the time, but we are lucky because the conditions don't kill people or it gets discovered later.