Even though the company closed, your 401k should still exist. Congress passed a law years ago called ERISA. That law requires that companies keep the pensions of their employees separate from their normal business accounts. Usually, pensions and 401k's are administered not by the companies but by third-party administrators such as banks or insurance companies. Try locating any old 401k statement that you have and look it over carefully to see if any bank or other financial company appears on them. That may be your administrator. If you can't find an old statement, go back over your old tax returns. Reference to the 401k may be in an old tax return schedule. Finally, contact the state revenuue office. Your old company had to file state tax returns. These returns may include info on which company was the administrator of the 401k.

There are two places where you might look. First, contact the Social Security Administration (SSA). A 401k plan is required to report any 'separated participants' to the SSA after about two years, if they did not take our their account.

If your account balance was small (especially if it was under $5,000) you might check to see whether the reported amounts were turned over to the state in which the company was located. Often 'small accounts' are 'escheated to the state' by banks and insurance companies. Retirement plans don't do this as often, but it does happen. Check with your home state website (the state where you lived when you worked for the company), and also check with the state where the company's corporate headquarters are located, if that is a different state.