Finding out the new reg on a car?

[MitchT]

I missed out on a great car back in March due to the logistical challenges of it being a nine hour round trip to look at it and someone else getting there first. Anyway, I figured I'd periodically check its "taxed" status, reasoning that if the car starts showing as "un-taxed" at some point then it's likely that a dealer has it and is about to advertise it for sale, so I can make sure I look out for it and get in first.

Anyway, when I check it now the vehicle tax check website just says "Vehicle details could not be found". The only logical explanation for this is that the person who bought it in March has put a different plate on it, so the vehicle is no longer discoverable via the old plate. Is there a way to find out what the new plate is?

I know if I do a vehicle check it will tell me about registration changes, but would it tell me the latest reg if I'm searching with an older one, or does it only tell you the registrations that preceded the one you're searching with? I know the VIN but I can't find a way of getting the reg number using that.

[worsy]

Surely the best way of checking now is if it returns to its original plate. Then you know the seller is prepping for sale.

[MitchT]

Possibly, though they might have just stuck one of those anonymous "dateless" plates on which they're not attached to enough to swap back or, as we've seen discussed on here a few times, people sell a car with a personal plate on and then try to retrieve it from the buyer after the car has changed hands.