inder said:They said they could not find any record of my reg number
If you've got "odd" plates that's no surprise; the system probably failed to read them. It obviously does take stills of plates it can't recognise though, and a human can work out from them what the reg. is.
I doubt they have the manpower to process all of these every day, so maybe you were just unlucky or maybe they were specifically looking for yours after you kindly told them you'd forgotten to pay?!