I tried to trace my first cars reg a few weeks ago and I got this reply from the DVLA which may explain !
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Thank you for your recent enquiry.
I am sorry but we have no record here for this mark 432DYM.
I should explain to you that the DVLA?s computer register was closed in 1983. After this, vehicles presented for registration were only allowed to display their original marks if they satisfied certain criteria. However, from 5 November 1990 the rules were changed to allow vehicles to display their original marks on a non-transferable basis, as long as applicants are able to supply documentary evidence to prove entitlement to the mark. However since your vehicle was stolen and never recovered it will not be possible for you to reclaim this mark and transfer the number on to your new vehicle
I trust the above information has been of help to you but if I can be of further assistance please do not hesitate to contact me.
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In other words I had no chance !
:xm