I worked for ASARCO LLC of Helena, MT. they closed in about 1998 (?) I believe I had a 401k plan but have been unable to locate where it is.Vanguard shows that the 401k's for ASARCO have been moved, they do not know where.
Vanguard may not know who the new plan administrator or custodian is but they would certainly know where the funds were transferred. Call them and request the name and address of the plan administrator. The funds may have been transferred to a bankruptcy trustee.
You can also check with the US Department of Labor abandoned plan website http://askebsa.dol.gov/AbandonedPlanSearch/ the National Registry of Unclaimed Retirement Benefits https://www.unclaimedretirementbenefits.com/ You can also check on http://missingmoney.com/
Good luck with your search
Hi there thanks for reaching out. You need to contact the human resources department of your former employer or the investment provider of the 401(k) plan. The contact information for the 401(k) provider can be found on your statements if one of those is available. Feel free to contact me via email to continue the conversation.