did you install a new fan or switch? if a switch, just wire it back up and dont worry, the fan is probably grounded in the junction box, and unless your house is newer then you won't have ground wires in other switches, its just that codes change. you'd have to do A LOT of work to ground it... he ground wouldn't come with the switch device, you'd have to supply it. in short i really wouldn't worry about it, you'd probably have to run the ground to the panel for it to be a true ground. if you're really unsure call a pro..
my dad owns an electrical contracting co and i worked for him for years.