I'm in Point Lookout now and blimey, krikey O'Reily, I've actually found no less than three things I haven't discovered before!
Thing #1 - A hidden box of shotgun shells behind some clipboards in the bank close to the pier. It was left alone.
Thing #2 - A lever-action rifle and a box of ammo on the road close to the wrecked truck. The rifle was left alone but ammo was taken.
Thing #3 - Two stimpaks and two boxes of ammo by the wall to the Ark and Dove Cathedral. Stimpaks was left alone but the ammo was taken.
I'm not sure if I actually missed these items before or if I have found them but didn't bother. But it does feel that I've overlooked them. Can't fathom how though