Should I be concerned about a buying a car with an unrecognised reg plate number?

I've found a 2012 car from a dealer with a number plate that is unrecognised on all the relevant websites. Might that be a cause for concern?

Asked on 14 March 2017 by charlie arkwright

Answered by Honest John
This is the correct government site to check: It could have had a personal reg that the previous keeper wanted to keep, so transferred it to a date related plate that they system does not yet recognise. On the other hand, there could be something seriously wrong. Unless this can be clarified I'd find another car.
Dear Honest John,

Please help me choose my next car. I would like it to have:
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