Some years ago a friend of mine got a call at home in Dorset from Bristol Police "Do you have a blue Asra reg number .............?"
She told them yes, it was at work with her husband. They asked if she could get her husband to confirm that, so she rang him at work then rang them back to say yes, he could see it in the car park from his office window. When she asked what it was about they said a vehicle matching it had been used in a robbery in Bristol, but it clearly wasn't theirs as there hadn't been time to drive from Bristol to Dorset. Never heard any more.
As to hiding the number plate in online photos, I don't see the point.