This happens a lot and unfortunately, it is out of the TDs hands, especially if the watches in question are hard to get hold of or very popular. It's likely the factory notified the TD that the watch was in stock when you ordered them but they then went out of stock in the day and a half or so between paying for them.
You can either wait a little longer and hope they come back in stock soon, change your order for something else, or request a refund. If you arent in a hurry I would wait for the other 2 to come back into stock or change them for something else to avoid paying for shipping twice (as I'm sure shipping can cover up to 3 watches max).