Hi there,
It has been reported that some servers may have rollbacked and admin/support cannot give your world back unless you downloaded your world before leaving.
It's also advice to ensure you save your world every once in a while or use "Skript" to have a auto-save in-place, now how do I set this up? Firstly, go to your panel and install "Skript" and then restart, when your server has restarted, go to file manager, "Skript", "scripts" and now create a new file named "autosave.sk", now open that file and put in the below.
every 5 minutes:
execute console command "/save-all"
After you saved it, make sure you are OP and run "/sk reload autosave" and now your world(s) will be saved every 5 minutes.