Yes you can forget to cycle a pump shotgun, just as you could forget to take off the safety on a semi auto or as you could forget to pull the trigger. When the pucker factor takes over and your sphincter muscle is puckering away with all its might it is easy to forget lots of things. That is why the NYPD, years ago, issued shotguns that they called Idiot Guns - double barreled shotgun, pull trigger it goes bang twice.
As for Jim Cirillo, a great guy, and a wonderful firearms instructor, very witty too.
best regards,
Glenn B