The British Pig Association maintains the record of pedigree registrations which are accessible to anyone on their website. Select the online herd book for OSB. If the pigs you have been offered have been registered they will certainly be listed there. The lost paperwork does not sound right to me. The BPA and their administrative processes are very efficient in my experience. Registrations are normally carried out online. I think I’m correct in saying that registration (which has to be submitted by the breeder, by the way) needs to be done within a year of birth.