Having worked at Radio Shack when I was 18 for a few months, I'm absolutely certain all of those incidents are true.
I have my own version of the sewage story. A few weeks before I quit, there was a large snow storm and the weather was doing the warm days, frozen nights routine. That caused a crack in the foundation which led to a flood in the basement, which was essentially the stock room. Some was kept on shelves, some in piles on the floor.
The day I showed up and was told of the flood, I went down to find 2+ feet of water with mice floating by on whatever merchandise was buoyant enough not to sink after being water logged for a week. Most of them were screaming little mouse screams, probably after watching their friends and family drown in the ice cold water.
Fast forward a week and the water was pumped out leaving just the smell of dead, rotting mice. Every time we needed to get stock to put out, we'd have to hunt around down there for half an hour, looking for inventory that had dried out to put on display for customers to purchase. It was never it's in intended location after floating to some other part of the huge basement.
A few weeks of selling soaked electronics later, they finally decided it was time to do an inventory and determine what was too damaged to sell and would need to be reordered. This involved spending 10 or so hours in the basement counting each and every item, some with dead mice and mouse shit in, on, and under the water logged boxes. I told the manager I quit and she proceeded to have a break down. She clearly didn't want to deal with all that by herself. I caved and helped her for a couple of hours before the I couldn't take the stench any longer and told her sorry, time for me to go.