Yes, I would use red Loctite on the swingarm nut. Also make sure that the nut is torqued down properly. I had the same thing happen, and I almost lost the swingarm, after the nut fell off, the bolt worked itself almost half way out. I was running wide open if 5th gear down a paved road, when I stopped, I saw the swingarm bolt sticking out. I got a new nut, and put plenty of red Loctite on the bolt, hasn't come loose since, and this is on a CR 500 powered quad that vibrates parts off constantly.
Yours truly, sincerelly, love always, Josh aka The DirtDemon.