Turns out after providing all the info supplied by Tsenecal and confronting another employee over at the local Home Depot, they determined they did have it in stock.
Seems as though there was some confusion regarding the request for closed cell foamboard, not many realize the term relating to the products they stock.
I did pickup a 4' x 8' x .75 sheet for only $12.67. Such a deal! hopefully it will serve the purpose, as I'm still not sure why another distributor wanted $40 for a 2' x 4' x 1" piece of what appears to be the same stuff. There may or may not be some slight difference between the two products, but I believe this foamboard made by Owens Corning should work fine. Only time will tell, Hey! the price was right that's for sure. If all else fails I'll use it for a bathroom wall project I have coming up.