Our most recent update secured the placement of buildings within a player’s base and secured the number of base expansions that a player had purchased. A part of this process was to stash any buildings that were outside of the legal buildable area, or had footprints that overlapped with one another.
If you believe you have a building missing from your base please check the buildings tab. You should see that these buildings are still available, they have only been stashed temporarily. Once you place the stashed buildings back into the legal buildable area you should be ready to go!