
The only way would be to contact the breed clubs and find out who owns the dogs where parents are missing.
I helped compile and correct aw friends IKC registered dogs pedigree by contacting the IKC with the names of the dogs whose parents were missing.
They were very helpful and I am sure the AKC would do the same.
With Scandinavian dogs you can freely access the Finnish database (Kioranet) and I think the Swedish one, though for NKK (Norwegian) you need to be a member.