I have several friends who through they were entitled to an occupational pension from their brief(ish) spells (2 to 8 years) outside teaching. All of them report serious issues extracting the pension from their former employers.
It seems to be standard practice for employers to claim to "have no records" from the 1970s and 1980s and to use this as an excuse for not paying pensions to former employees.
Maybe their former employers no longer have records, but the pension providers will. Can they find out which pension provider they were with and contact them direct? There should have been paperwork sent out to the employees at some time with the details.
The alternative would be to contact an Independent Financial Adviser, although they might charge for the service.