You can find the seed if you have access to the servers FTP. If you don't have access to it, you simply can't.
If you do have access to it, download the .fwl file from the server (I use FileZilla to access it).
After it's downloaded, just go to any hex editor and open the file with that, online ones work just fine (I use hexed.it).
You'll see letters come up on the right hand side, marked with red in the picture, and that's the seed.
Seeds have a max character limit of 10, so if there's more characters after the 10th, it's not for the seed. (In this case I have a H after the last character in my seed.)