I know Tilbo is frothing at the mouth again about people with drones but..
someone called in a sighting, correct? An unconfirmed sighting, presumably, given the short amount of time the airport was closed.
At this point I imagine this was a hoax call - you know, the same thing idiots have been doing for decades, since the invention of the telephone, for shits and giggles. "Hurr hurr, let's see if they shut Heathrow like they did Gatwick, hurr hurr *dials 999*"
I could call in a sighting about a remote controlled aircraft; I bet the same thing would happen.
I could call in a sighting about someone with an RPG; I bet the same thing would happen.
I could call in a sighting of a caravan parked on the runway .. ok, ok, I guess ATC would be able to spot that as a hoax pretty quickly
Still, if we're banning things, let's ban caravans before we ban drones