I had the same problem earlier this year on a fabric I selected. I understand that mills have closed. I found a second fabric and was told again (local furniture store for sherrill) my second selection was discontinued, BUT, when I contacted Boyles, the sales person actually contacted sherrill directly and sherrill had enough fabric in their stock for my sofa & wing chair. I ended up purchasing all my furniture for our new home from Boyles.
As far as trying to find the mill....I tried that too and was not able to find.
Best of luck.

There are a number of fabric wholesalers in High Point, NC that buy discontinued patterns from factories and then sell to the public. The largest one is called 1502. You might try there. First, though, I would call Sherrill and ask to speak with their fabric buyer. He (or she) should be able to tell you whether they have any fabric remaining or to whom they sold off their excess stock.