Disappeared pension

I worked for a company called grey security services for almost 5 years from 1988 to 1991 i was paying pension i resigned from them i never got my pension l was told that Grey was bought by G4 . i was told to ask Absa pensions they referred me to another company that company as well referred me back to Absa neither G4 could help l endeded up losing my pension including the lump excess that might have been paid by Alexander forbes all i want is some one to tell me what happened to my pension