The way the brain works it is easy to understand how this happens. Your brain looks for all the parts - all present - all in the right general area - everything must be fine...
I remember when doing training for my ppl, doing FREDA/down wind checks... Saying everything was in the green.
My instructor quickly coveed up the panel and asked me to
tell him the temps and fuel qty I had observed 'in the green'
I realized I had been caught with my pants down, and now extend my check to not just confirm if the needle is in the green, but what the actual value is as well.
I can see how at quick glance one could see the incorrect harness as 'in the green'.