[sorry...I meant to post the above as an answer, rather than a comment...]
For a tax refund, the Atencio's might be out of luck.
The IRS website notes:
Time Running Out for Some Unclaimed Refunds
"The law provides most taxpayers with a three-year window of
opportunity for claiming a refund. If no return is filed to claim the
refund within three years, the money becomes property of the U.S.
However, there are other unclaimed federal funds for which they may be
eligible. Each federal agency has a different set of procedures for
making a claim. You can explore them one by one using the links here:
Government May Owe You Money
"Check unclaimed property, credit unions, mortgage refunds and more..."
The site includes links to IRS sites, in case you want to pursue the
matter with them further regarding the unclaimed funds in question.
It also has links to instructions for unclaimed funds regarding:
Mortgage Insurance Refunds
Federal Employee Benefits
and also includes links to individual state sites for investigating
the status of unclaimed funds in the states (bank accounts, etc).
I trust this information fully answers your question. But before
rating this answer, please let me know if you need any additional
information. Just post a Request for Clarification, and I'll be
happy to assist you further.
Best of luck,
search strategy: Used bookmarked links to federal Unclaimed funds sites.