The game isn't even out, yet. There was a problem with the game boxes, so the release was delayed. It will come out in the upcoming weeks, though.
Viewing post in Dango Dash (Game Jam Edition) comments
Then I apologise, although it's pretty bad from a UX perspective to write "SOLD OUT" (instead of something like "Pre-Order") underneath the product imho but I guess this isn't your fault. :) Looking forward to your release.
Edit: Well, apparently they changed it now. Also I subscribed to the mail notification to get an alert when it's out. :)