Well can't say for certain what caused it's untimely demise, but a few things I would advise changing for you next setup.
1. More substrate. Emperors burrow. They are hard wired by nature to do so. Even when provided with a hide they will burrow underneath it. You should provide at least 15cm of substrate for an adult emperor.
2. Heat mats under the tank are a big no no. In order to properly regulate their body temperature they burrow. Down the burrow to cool off, and up to get warmer. Under tank heaters mess with their natural inclination to retreat away from the heat. They will go down the burrow and just get hotter and hotter which can lead to a steamed scorpion. The best place for a UTH is on the side of the enclosure, but better than that is a heat bulb. Get an infrared one. They do not see red light so it won't disrupt their nocturnal activities, and there are no harmful UV rays.
3. Ventilation is good. Despite what you may read about keeping humidity through restricted ventilation, it is not good. They need fresh air. Keep humidity up with a false bottom setup.
Finally, here is a
care sheat for your Emperor. This includes a link that details how to set up a false bottom.
Oh, and don't listen to the dummies ate the pet shop. 99% of the time they have no idea what they are talking about.
Best of luck with your future friend!
