This is a true story, several years ago there was a comment that M13 wasn’t listed in the back of Interstellarium atlas, so I checked it out to be sure. From what I could gather I was unable to find it either. It may very well have been in there but neither of us found it. What cracked me up though is this CN member didn’t want to buy the atlas mainly because of this. It had nothing to do with any concerns of errors because it’s still an amazing atlas with very few error in the grand scheme and most atlases have errors anyway so it’s no big deal.
I have to say though that amazes me that anyone would worry about such an overly played out object. I even thought if I ever made my own atlas I’d go as far as to omit M13 so people would stop staring at just showpieces and spend more time with M92 instead just to shake people off M13 for a change. Amazes me how many just stare at the same object night after night and ignore so many other incredibly overlooked objects.