You do still have the stock. You can sell it if you want to. You need to find out what broker that Walmart uses for those kinds of employee funds.
Fidelity is one of the most commonly used ones. You should have been getting some kind of statements from the investment broker showing how many stocks had been purchased for your account and the value of those stocks.
Contact the HR person of your local store if you can not locate the information. They should be able to give you a phone number to call to get the information that you need.
If you purchased stock then you always have it, the company doesn't even control that.
How do I find out I still have stock and can I sell the stock if I still have the stock?
