Lee Cockerell who was once Executive Vice President of Operations of WDW said he didn't care about the refillable mugs, use them as much as you like.
If Disney can no longer be bothered to make original designs every year, or make them resort specific like they used to, they no longer care IMHO, no matter what signs they put up.
So if they haven't changed the design by June next year, I will sure as heck use them again. It would be Disney's fault for not changing the design, they can't tell.
If they do change the design, I would buy new ones, cause that means they are actually playing an active role in deterring it.
Just my 2 pence worth.
To the OP: I am sorry your mug got broken, that really sucks! They are great to use at home.