Hi yesterday i had a player called xXMRCheetahXx in my warp shop while skyping with a titan called : RavenMischke and that guy cheeta was coming on my sky block the whole time on my island not in the shop and he could go in my chest and everything but i didn't invite him so i banned him from my island but he still did come and he was looting al my chest when the titan was next to him so now i come online and all of my farms automatic ones and fish farm are destroyed and he destroyed my shop here's some screens:

 

I am sorry, without proof of the person actually griefing there is nothing we can do. Also, to add.... the only way someone can destroy anything on your island (besides animals and crops) is because you added them. By adding them you give them all rights to the island and if they choose to destroy it they can because you allowed them to be able to. If you don't trust them, don't add them.