I dunno. On mine that sucker is on the spring and isn't going anywhere. I don't know if they use any glue to keep it in place (I doubt it) but I'm not about to yank on mine any further to see if/when it will come off. If anything, if it's a problem I would be inclined to stretch out that end of the spring a bit, increasing it's diameter, to get a tighter fit for the insulator.
If it isn't a problem when you get your K100 I wouldn't be concerned about it. If it does become a problem try manipulating the spring to see if you can get the insulator to stay in place. Once you have a battery in there and screw things together though the insulator can't come out of place. Chances are if it could manage to pop off before you got it screwed down to fit your battery of choice, the out of place insulator would prevent it from firing at all by being in the way.