I have talked to a few registry members who had assumed they had their original blocks - until I called them & told them their original blocks had surfaced.
Some were pulled & replaced early on when the original or later owners had them & they just kept the damaged engines.
For anyone with an AAR or T/A, if you have not checked to see if your numbers matching motor has been reported yet, send me an email.
Same if you have an AAR or T/A block loose or in a car with a partial VIN on it.
Several engines & some transmissions have been reunited with their original cars in the last 20 years, it does happen.