If you're the owner of the island and you haven't logged in for some time you get the warning message when you first rejoin, or if you just created an island you will see it. It will stop on the next login all by itself. Though to be through we can check if you give us your In Game Name (IGN)
Your island is safe, if the message appears at the next login feel free to let us know, but it does appear you received it as a first login.