I wanted to start a new kingdom today, and decided to see what would happen if I used the same name as my main kingdom. I created the new kingdom, and it promptly "overrode" my main kingdom...
Luckily I still had my offline save from my Gog version of the game, and I managed to "recover" my old kingdom.
I was rather surprised that there was no override prompt.
I've done this as well, but unfortunately the way I synced I lost my kingdom permanently. I actually didn't even want to sync at all, I just wanted to log in to play the dailies, but there's apparently no confirmation on cloud syncing.