Update: This appears to have been fixed!
Hey Howdy Hey Tappers!
Just a quick note that it appears that the Santa’s Wonderland box is glitched. It seems as though, for some players, when you still have 1 item left in the box it disappears. This shouldn’t happen, and if it’s happened to you it’s a glitch.
The best thing I can tell you to do is report it to EA. You can do so here. Hopefully, this will be patched soon.