I'm 100% sure it won't let them as it runs the same check as if they just clicked on it. I'm sure vBulletin has it built in the attatchments php file.
Anyway, keeping SRL off google won't do anything. I'm pretty sure even now it's very hard to find a common way of putting runescape hack into google and getting SRL anywhere near the front, so there's not much point in using a Robots.txt to make them avoid half the forum. Anyway, I'm pretty sure the bots only get access to the un-registered users stuff, so not much to loose from there.
By reading this signature you agree that mixster is superior to you in each and every way except the bad ways but including the really bad ways.