Have you checked every sub category of your inventory? The SHOULD be under Buildings. That's where they go when I store mine to stop an error.
Otherwise you'll just have to wait for Tech Support to help you. It may take a few days (or weeks) before they can get it straightened out. I had the "Homer can't work at the City Dump" issue in one of my games and it seemed like forever before they got it fixed.
We are not employees of EA so there is nothing that we can do to help you any faster. Especially since you have already done the main thing we would have recommended that you do, which is to contact EA directly. Aside from that all we would recommend is double checking your entire inventory, visiting Krustyland or Other Springfield, force closing all apps on your device, restarting your device and uninstalling / reinstalling the game.
TL:DR If EA are working on it... wait for them to finish working on it.