Can you explain the metaphor "hiding the umbrella"? Google didn't turn up any obvious meaning. If I had to guess, it's a reference to the joke about turning in

Can you explain the metaphor "hiding the umbrella"? Google didn't turn up any obvious meaning. If I had to guess, it's a reference to the joke about turning in your expense report, after being told they won't reimburse you for the umbrella you lost, and so you overstaet expenses enough to cover the umbrella's cost. But that never made sense to me, since they demand receipts anyway...