I've not even wore a system yet, but I think that the chances of this happening are really really slim in real-life, someone really tugging on your hair.
I've read a few posts on here of people who wear and have had people touch their hair, and it has managed to stay on.

Think about your own hair, and in the past, if people have touched it. You're more likely to have a hat grabbed off your head than your hair getting touched. For a while, when my hair was really awful (I tried cutting it at home but ended up thinning it too much etc) So, I wore a baseball cap or a beanie out a few times, and especially if alcohol is involved, the amount of folk who had to try on the hat, or take it off.

I'm not that fussed about someone tugging on my hair, or touching it. I plan to stick gel or wax in my hair, and I doubt most folk would want to touch it with all that in it.

I can see your worries though, last thing you want is an almost perfect undecetable system then some crazy bint pulls it off on the dance floor!