Assuming you had avoided congested areas and crowds, even at 800-1000' you are in the clear, whether or not he had your aircraft reg matters not.
This may well be urban myth but i'll tell it anyway. There was a farmer who became so pee'd off with aircraft flying low over his land that on the roof of a barn he wrote some abusive wording directed at the local raf fly boys.
This became well known with in this particular force and instead of detering aircraft from flying over this farmers land the barn became a checkpoint for first time solo pilots who on return to base had to recount what was written on said roof.