Everyone misses something sometime... thats why we all gather around the new plane (no matter WHO put it together) and go over it.
A couple of weeks ago someone found my elevator servo arm screw was missing. A few days before that I found some loose hinges on a new model by a VERY experienced builder (he just forgot to glue em...[&:])
You'd think that guys that have been building them for 30 years would no longer make mistakes... But nooooooo

We make some of the same dumb little mistakes any beginner can make. We're just smart enough to have some other guy help us find the errors before we try to fly it.