I have never heard of any story where someone calls the cops saying someone had a gun and it was really a gun.
Two years ago, I think, guy walking around the mall. Some dip**** calls the cops saying that someone is walking around with a samurai sword across his back. SWAT teams, cops, evacuation, etc they tear the mall apart looking for him.
The "suspect" walked out of the mall going about his business. He goes back to work where he sees the news and all the hoopla. Says to himself " holy crap that's me". Goes back to the mall and turns himself in.
It was an umbrella. If I remember correctly it wasn't one of those that looks like an actual samurai sword.
Lots of time and money wasted for nothing.