Hmmm... Sorry to say it, Captain, but I think that you are experiencing a phenomenon not uncommon to collectors, the "dream merchandise" syndrome...! ;-)
Just like the pristine row of Tintin text novels I clearly remember finding on a shelf in my favourite bookshop in Aberdeen, I think that your posters may be no more than a combination of sleep and wishful thinking! I can see them still, and know I held them, but sadly... :-)
I can't rule it out categorically, but as far as I know the only book-cover posters ever to see official release have been the French ones.
It's possible that the shop printed something up themselves (naughty naughty!), or that there was some promotional material made at some point (perhaps Little Brown wanted to publicize the American editions), but as far as official merchandise goes, the French posters are it, certainly at this current moment! | 
