There are many questions you need to answer. Where did you get your glider? Did it look healthy when you got it? How old was your glider? (A glider's tail should be fluffy not smooth when you get one. If it's tail was smooth then it was too young to be removed from its parents) What temperature was the room it was in? What type of bedding did you use? (Pine bedding is toxic) What where you feeding it? What type of cage did you get, with what type of coating on the bars?
It sounds like the pet store doesn't know much about gliders. Only eating from your hand and waiting a week to interact with them is ridiculous. When you buy a glider they should be eating from a bowl. Gliders should never be sold alone. Gliders can self mutilate from being lonely. Always get at least two gliders.
Sorry to hear about your loss. It is possible that the glider was sick before you got it. If you choose to get gliders again do a little more research before getting them. Always get more than one. The only safe material to put in the cage is fleece. So no more socks. The getting a sleeping pouch made from fleece and hang it in the cage. Look at the diet page on this website to learn of approved diets for gliders. Look up some glider safe wheels, because most other wheels including wodent wheels can be dangerous for gliders. Try looking at some glider safe cages. After getting a glider bring them to the vet for a wellness check, just to be sure that they are ok. If you notice that they aren't eating or sleeping well take them to the vet asap.