Who gave you the stock? Check with them because either they got a physical stock certificate (a printed document) or the account is being held for you in a brokerage.
Was the stock in your parents' names as a "custodial" account? If so, ask them.
You should recall the NAME of the corporation that the stock was for (for instance, AT&T, IBM, General Mills, or several thousands of other corporations), contact the corporation's HEADQUARTERS and ask for the shareholder relations dept. They can help you.
If you don't know anything else, each state has a list of abandoned assets and they might be able to help you.
Let this be a lesson to you: ALWAYS ALWAYS ALWAYS save anything that has to do with investments.