To save a world between computers and websites you have to use "export" and then on the other computer or website use "import" and select the correct save file. (Sorry if it seems complicated, i am bad at explaining things).
Unfortunately creating cloud saves is quite complicated (Itch doesn't offer a service for that afaik), but I totally understand that it is would be frustrating to lose such a nice save file! On Android, you should still be able to Export and Import save files via the menu. On iOS, this is unfortunately impossible because iOS doesn't want to play nicely with these files.
I will see what I can do though!