Do I need an attorney to find out the status of a bankruptcy case?
We know the company in question filed for Chapter 11.

Now their phone is disconnected and a credit report says that the business is no longer operating at the address where we sold.

Answer:
A good starting point would be to contact the Bankruptcy Court where the debtor filed their Chapter 11 bankruptcy and ask the Clerk of the Court for information about the status of the case. The following link contains the name and address of all the U.S. Bankruptcy Courts: http://www.bankruptcydata.com/Courts/Courts.htm