Workers should have been wearing masks to prevent inhailation of glass particles. In future washings the fibers then redeposit back into the clothing being washed. I don't think there is anything you can do to completely remove the fibers. In the past consumers were warned never to wash glass fiber curtains in their home washing machines. You could tell if the fibers were glass by looking at them under the microscope and comparing what you see with photomicrographs.
Asbestos fiber looks quite different than glass fiber.
In a burning test neither will burn nor support combustion. I have not heard of asbestos being used in draperies because the fibers are very short and would have be blended with something else to have the flexibility that draperies require.