At least one listing that is still active does indeed include a picture of a Kmart receipt. It seems the company got wise to the error, as all the locations we called reported the November 8 release. We suppose if you really want MW3 five days early, you might be able to snag one. Of course, that's assuming you're willing to pay upwards of $100 and the listing survives underneath eBay's watchful gaze.
Incidentally, if you find yourself with a legitimate retail Xbox copy, don't worry about playing it early. Stephen Toulouse, Microsoft's Xbox Live guru, has given the all-clear on Twitter.
Update: Stephen Toulouse has posted a new update on Twitter, stating that Activision has not authorized pre-release play of Modern Warfare 3. According to Toulouse, "Playing early may impact your account!" Seems a bit unfair to anyone who may have legitimately purchased the game from a retailer, but there you go.
Update 2: Now Both Infinity Ward Community Dude Robert Bowling and Mr. Toulouse have clarified that players with early copies of Modern Warfare 3 will not be banned or otherwise punished for playing the game online. We think. Who can tell at this point?