I can't get rid of the mod

I recently downloaded a HL2 mod, "Research and Development" and I've beat it and want to get rid of it, but it's not in the control panel's "add or remove" list, and when I right click it in my Steam Games List, it gives me no option to delete local content.

halp plz?

just go into your steam folder and delete it.

It's a sneaky bastard, there's no

EDIT: IVE FOUND THE FUGITIVE AND NOW UNLEASHING MY JUSTIFIED WRATH.

DEATH PENALTY MOTHER FUCKER!