.... what's important in the visa is the entry stamp, hopefully technology was in good use when you came in and they have actually kept record of people that came into this country when you came in.

In any case, if you can prove you being here before the age of 15 without leaving much doubt, you should be good, education, vaccination or medical records should be a good way to go, I imagine even when an ITIN number was issued might work, maybe.