No idea why they would delete your video... Or why they even have the right to view it?
If you were seriously out of a busy area and minding your own I can't see why after they realized what you were up to that they wouldn't have just at least only told you it wasn't a good idea and set you on your way, as what you were doing isn't exactly illegal... Hell, you could almost do it with a real fire arm and get away with it, not that you should EVER point even a BB gun at a person.
As a kid I used to walk past the 6 houses on my street with my pellet gun in hand to the bush lot and fields at the end of the street to go in and shoot at whatever, and there were people that were walking around in there on the trails all the time. I would just cock the gun so the barrel was obviously open, let the people go by and then continue my fun. Not once did I ever have a cop show up at the door or stop me.
These days, I'm afraid about the 50 feet between the front door and the back of my truck when I have my gun in a case and I'm going hunting, if someone driving by or a neighbour sees it if I'll have cops pulling me over once I get on the road.
Man do I ever hate this over sensitive society we live in!