Guarantor on mortgage, need proof

A friend of mine was guarantor on a mortgage in 1986 and the mort was paid off in 2006, would there be any way of getting proof of this? He doesn't have any paperwork from 1986 and has not contacted the mort comp yet (but will do) - or would it show up on something like Equifax? Seems strange that even when someone does something like this, their name never appears on the deeds or documents :(

Any help or suggestions appreciated, thanks.