Ron, it’s the other way around when a problem typically develops.
Posting the VIN of a car and saying you need the Z28 or L78 or whatever engine, then someone can make up an engine, restamp it and then it’s a problem.
If you post the VIN on the engine, there is only one match. No problem.
Usually what happened when there is an orphan engine is the car was wrecked. But there are cases where car and engine have been reunited.