If you don't know the name of the life insurance company, check for past premium payments that were made through a checking account, check book receipt stubs, or other bank accounts. Also, check with findyourpolicy.com which may have a record of the life insurance policy.
See if you can find a recent premium notice, checkbook, or check to see if any money has been withdrawn to pay a premium on the life insurance policy. Check past bank statements for checks made out to any insurance companies. Those items frequently have the policy number written on the check.
If you cannot locate your own life insurance policy just write to the life insurance company and tell them that you lost your policy. They will be glad to send you a copy of your own life insurance policy.