1985 Other Volkswagen Models tranny failed

I was driving along in my vanagon.I believe that I was in third gear. It seemed to have popped out of gear.I clutched it and put it back into gear to find that none of the gears where there. There was no grinding. After coasting to a stop.I can shift through all of the gears without using the clutch. There is still no grinding.I checked the linkage and it is intact up to the tranny housing. I have not had any problems with it slipping out of gear in the past. Thanks so much for you time and help!