I've learned to never say never. There is a lot of turnover in fast food, including in management. Years down the road the management at all levels could be extremely different. I will say that, if this had happened to me, it would take a LOT for this particular location -- and possibly the franchisee or even the entire chain -- to earn my business back.
Like the OP, I would be in contact with the restaurant manager (assuming that was not the restaurant manager there at the time), the district manager, the franchise owner if it's a franchise, and eventually the corporate offices. I'd also be calling the health department in the meantime. If the DM was unresponsive, then I'd be calling the media outlets.
It's not just what was found, but the reactions. The MOD and the employees acted like it was a joke they planted. That's not something you joke with. What if YOU had been the health inspector just stopping in for dinner? They'd be up a certain creek without even a boat much less a paddle.