I have an offer from an employer in Texas, everything turned out okay except when they look up for my SSN, they said it turns out as "no match found"
A little backstory:
I'm a Mexican Citizen, came to the states for college, legally(fees, visas, tests), graduated in 2013 and applied for an OPT permit, which allows me to work in the US for a year. When I received my OPT card I went ahead and asked for a SSN at the SSA office, when I get there and give my information, turns out I've had a SSN since 1990(I was a year old) I'm not sure why I had one but afterwards I asked my family and said one of my uncles got it for me(still not sure why). At the SSA Office they told me I would keep this number since it was already associated to my name. So on May 2014 I got my SSN Card. The OPT card expired on Jan 21, 2015 and that was the date I returned to Mexico, turned my I-96 form(I think its I-96 or I-94, it's the permit for entrance to the country) and got my Student Visa voided and I've been living in Mexico ever since.
Now I have applied for a job in Texas and well the rest is explained in the first sentence, employer asked to look and see if I have a DHS authorization for this SSN, I have all my paperwork saved(even envelopes) but I can't stop thinking that someone might've thrown something out, or that I never got an authorization letter for this number. I can't avoid panicking a bit, so I wanted to ask what should I do in the case that I don't find this DHS authorization.
PS: The SSN card says VALID FOR WORK ONLY WITH DHS AUTHORIZATION