It's a glitch. When redesigning, it's best to NEVER place any of your buildings into your inventory. Just move them somewhere til you're ready to place it where you want . Many people have written about placing limited time buildings into their inventory and having them disappear, and not being able to get them back, or having to rebuy them with donuts. After the Christmas event ended, my friend placed the
Bowlarama into his inventory, and it was gone, back in the store. He had to rebuy it with donuts and was very unhappy lol.