I would contact whomever was the administrator (start with fidelity, they're the most popular). It may take some digging, but the accounts could been passed to a 3rd party clearinghouse. Also check with whoever did your payroll at those hobs (ADP, paychex, etc) to see if they have records, be it paystubs, withdrawal authorization forms you may have signed, or w2 forms from previous tax years. Any retirement withdrawals would be a line item sonce they came out pre tax, typically