Sand down the 'post' that the stop sits on w/rough sandpaper then thoroughly cleanoff all grit/dust. Nowglue the rubberstop on w/3M weatherstrip adhesive. Let it sit overnite.
I have a 2006 and just noticed that after my weekend of riding I no longer have that rubber stop either. I guess when I replace it I'll try some sort of glue to help keep it on.
Sand down the 'post' that the stop sits on w/rough sandpaper then thoroughly cleanoff all grit/dust. Nowglue the rubberstop on w/3M weatherstrip adhesive. Let it sit overnite.
I can't say for sure what it looks like but a friend of mine said he put a small brake pad off a bicicle ( one that has a bolt on it ) through the hole and cured his from folling off forever. I gotta check it out. Hasn't happened to my bike yet but worth remembering.