Your lua folder isn’t there by default. GMod takes its resources from the GCFs. Also, you should use addon folders, not put things directly in the lua folder.
He probably has a pirated GMod.
Doesn’t look like that, judging from his Steam profile.
If there’s ever a folder missing in your GMod folder, it doesn’t hurt to create it. Just remember to make sure it’s all in lowercase.
I got it back now… but thx anyway:D