Replacing an electrical outlet without the ground!

[Rasha Gish]

Can anyone share the best way to replace an outlet with/out a ground wire?  It was suppose to be a straight forward project but I managed to pull the green ground wire out of the box while I was replacing the old receptacle!  I can't see where it came from, I really can't see any bundles I think its behind the box.  I connected the black wires in a nut and the white wires in a nut and closed the outlet, but unfortunately the outlets down the line are showing "no ground" on the tester!  Would installing a GFCI in that outlet protect the outlets down the line? Or do you think taking out the box and searching for that ground bundle is the best way?