Yep, if you can't see them, they can't see you, so you are not helping.
A buddy that gets a little rammy was backing into a site. Another buddy was on the other side guiding him. The driver was ignoring me and watching the other guy. Problem was, I was trying to get him to stop from running into a HUGE rock, but he never looked at me. It was all clear on the other side, so he just smashed into the rock on my side!
Moral of the story is to look at both sides, and both helpers if there are 2. Then maybe get out and look if any doubt at all.
Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!