Simple solution that would have avoided that death - NO WATER DISH in the display tank.
Seriously, if that was allowed in a publically viewable display tank, what the hell is going on "out back" in the STAFF ONLY ACCESS areas of these shops ?
Bearded dragons DON"T NEED a water dish if fed live insects and fresh veg and occasionally given a drink.
I'd be following up, and sending a letter and copy of the image to the local paper's editor too , heck maybe even a nationally read newspaper , and TV station news team …. these people need to be shamed publically and give VERY BAD PUBLICITY.
If people like us here don't advocate for these beautiful but defenseless creatures , then no one else will.