Driver Error

How can anyone approach a car (truck, really) open the door handle which is seen on the left in the first picture, and not notice the gas cap cover is open?

I don't know, but I did. Perhaps if I had walked to the car from the back I would have seen the "traffic cone" orange funnel sticking in the opening.

It seems L. was adding some additive to the gas tank. We backed out, drove merrily on our way to the first stop sign and a kind man pulled across the intersection on his way north, slowed and told us our gas cap cover was open. How thoughtful and nice! We pulled into a church parking lot and
removed the funnel, replaced the cap and closed the cover.

Perhaps we should take an observation walk around the vehicle like pilots do before they take off.

(These photos were staged to illustrate the incident.)