Vehicle Identification Number (VIN)

Hello fellow inventors and DIY enthusiasts,
When I browse this forum, I get the impression that only experts in mechanics and electronics are active, and I can only marvel at their knowledge.
I hope to solve the following problem with your help.
I installed a TDI PD engine with 74 kW in my T3 van.
(I've driven approximately 10,000 km with it so far, and it runs great.)
In addition to the engine, the gas pedal, the dashboard insert, the steering column levers, and the complete steering column with ignition switch were also modified.
The donor vehicle was a Golf IV, manufactured in 2000.
To duplicate a second ignition key, I need the vehicle identification number (VIN) of the donor vehicle, which I unfortunately can no longer obtain.
Data regarding the engine are located on the timing belt cover.
I believe it should be possible to determine the vehicle identification number (VIN) based on this engine data.
Following a request, Volkswagen refused to provide me with the information I was seeking, citing data privacy reasons.
Does anyone have any tips for me?
Best regards, Hoin.