Try emptying the cache on your browser and then reloading the page. Also check the "timestamp" date and time. It may be that the post is set to appear in the future. Also under options > general, make sure that the adjustment to the UTC time is correct for your time zone.
I would also suggest that you review the terms of service here at wordpress.com since we are not allowed to sell things on our blogs here at wordpress.com. They are non-commercial.
I suggest that you contact staff at http://wordpress.com/contact-support 9am-5pm Monday-Friday, Pacific time for an official ruling on this, but I've seen blogs suspended or deleted for selling things on them