It was the 45 ACP Full Size if I remember right. How that one episode could create so much buzz to wipe out S&W's entire M&P inventory... Always fun to hear what story a retail worker will cough up.
M&P's are not impossible to find but they have gotten rather rare... No more can you pick a model from the website and rely that you'll be able to find it in town or online right away. You either have to bend to what's in stock or wait indefinitely...
The M&P 22 is a different animal. It' newish, and it's manufactured by Walther. The 2nd run of those guns is out now and you should be able to find it online almost anywhere and probably soon in most gun shops that stock M&P.