Buildings that have been spawned don't have an infinite lifetime variable. It has been mentioned before to fine the spawned item in your types.xml file and change the lifetime parameter to 3888000 to keep the spawned object through a server restart, otherwise it will be removed with the restart. Your other option would be to use the traders mod and edit the files in there to spawn a new building every time the server is restarted, the catch here: you may not want to have anything placed in the building when the server is restarted or the placement may not work correctly. (I have yet to confirm this but I am stating it to be a cautionary!) The benefit of using the traders mod is that you can also adjust the buildings rotation, which you currently are unable to accomplish with Community Online Tools...YET. Just food for thought.