This story, about a crook holding up an ice cream shop and not being able to open the register, reminded me very much of a story my dad used to tell when my parents owned a liquor store:

A friend had recently opened another store in a different part of town. My dad helped them close the place down one night, and noticed the owner locking the cash registers after he'd emptied them. "You really don't want to do that", he said.

"Why not?" the owner replied. "It's got a lock, I want to make sure everything's secure."

"Because crooks are morons, and they'll think there's something in them if they're locked. It's better to leave them with the empty drawers open. The thieves will just ignore them."

Apparently the store owner ignored the advice, and sure enough a few months later his store was broken into and two empty cash registers (costing thousands of dollars each) were destroyed by thieves smashing them to bits trying to get at what was inside.