There is no life assurance equivalent of the "dormant accounts" legislation, so life assurance companies do keep records of policies that are still live. Live would include policies that have a surrender ("cash-in") value even if premiums haven't been paid for years. Name and date of birth should be sufficient to locate a person, being careful if there are possible alternate spellings of the name (Brigid, Bridget etc.) and trying maiden names if applicable.
If, as Complainer suggests, a policy was for cover only (and had no surrender value), the cover will lapse after a period of non-payment of premiums. A life assurance company will not keep records of such a policy beyond a certain number of years, as it has no value to anyone.