When pension plans first became a popular benefit in the U.S. it was normal for people to stay employed by the same company throughout almost their entire working life. This held true when employers began switching from traditional pensions to 401(k) accounts. However, that is no longer the case for many working Americans.
People today change employers frequently.
That often means they have old retirement accounts setup at previous places of employment. If someone is not diligent in transferring those accounts when they change jobs, the old accounts can become forgotten or lost. That can make it difficult to later find those accounts when needed, such as when retiring or administering an estate.
This problem was discussed in a Wills, Trusts & Estates Prof Blog article titled "How to Find Your Lost 401(k)."
Currently the U.S. Pension Benefit Guaranty Corp. has a database of traditional pension plans that allows people to find any lost accounts. The agency would like to make that database easier to search and would like to expand it to include defined-contribution pensions and 401(k) accounts.
However, for now, inclusion of 401(k) accounts would be voluntary and there are other companies attempting to corner the market. A bill is in Congress that would make it mandatory to create a nationwide searchable database.
If you have old retirement accounts you cannot locate, you might want to contact your representative in Congress to urge passage of the bill.
Reference: Wills, Trusts & Estates Prof Blog (Sept. 20, 2016) "How to Find Your Lost 401(k)."