Same thing happened to me as well. I ordered Fitbit (even though i had the same offer in other sites I ordered in walmart cos i was ordering other stuffs as well) and other items like PenDrives HardDisk.
They cancelled the Items one by one (not all on the same day but 1-2 days apart about 2 days after i placed the order) saying the Item is not available. Lucky for me i had other similar options still available. They could have at least kept the order for future inventory(or pick from a different store) rather than cancelling it. Had to search for similar offers and place the order.
Hated the experience shopping in walmart online. I will never ordering there again.
Reviewer is in unhappy mood. Please immediately contact the author of this review to discuss order processing issue of fitbit flex wireless band. Walmart needs to offer any options to resolve the issue according to poster's claims.
Other people also mentioned fitbit flex wireless band in their reviews. You may find this information helpful for further shopping at Walmart. You can also consider other company suggested by the author: Target.