How to get a tough spot off an LCD?

[Uberbob102000]

I let my little brother use my computer because his broke and he got a splotch on my monitor that I can't seem to get off. I've tried everything from lens cleaner to Isopropyl alcohol. Any suggestions?

 

[SH1]

I was told by a tech to just use a soft cloth. (With, for more serious spots, a mist of distilled water...)

You've already used more serious cleaners, so, well, I wonder if it is some kind of scratch?
Hopefully not though...