As bad as it is, and through years of witnessing similair situations;
1. Was your hat on the game before Nathan blatantly edited and got it uploaded to the server
2. Is the hat you made patented
If the answer for both of these is yes, you will probably get a solution in your favour.
If your answer for both is no, GraalOnline would not care If you made the original concept for the hat. Especially since the hat was edited and recoloured and not EXACTLY a completely stolen piece of artwork. As stated before in the thread - anything that's uploaded to GraalOnline is therefore owned by GraalOnline, if your version of the hat has not been uploaded or is not patented what does GraalOnline benefit from resolving this particular case of plagiarism?
(Too lazy to change GraalOnline, read Toonslab instead)