Thanks for the suggestions guys, but still haven't found it.
Checked:
1. Sway Bar End Links (They're now Teraflex Quick Discos, but checked anyway)
2. Shock Lower Mounts
3. Bumper Mounts
All my mods nuts or bolts have paint marks across them. None of them look like they've turned. I've also tried to feel behind any bolts also to see if the nut is missing off a bolt... Nothing so far. All critical components look ok, but I'm still new to this JK thing and could have missed something. This is definitely the same size as a lower shock mount nut, because I test fitted it.
Any other suggestions? I have a Teraflex LCG Elite Lift if that helps.
Thanks again.