Did anybody change the level name on the dashboard? If so, change it back to whatever the world was called. If you never uploaded a custom world, the default world name will be world.
I assume you're trying to make a bedwars or skewers type mini game, if you're using a plugin for these, it'll most likely have feature for this. There is no other plugin where it'll refill chests. You could try writing a Skript that does this.
A few things.
If you have any evidence, you can report them [here].
You can also enable something called a Whitelist, which means only trusted players can join. Read up on this [here].