I did a quick test on my local instance, but I’m afraid I can’t duplicate the problem. Maybe check the browser console for errors? Perhaps the name is using some special character that looks like the normal “mcs-mem” characters but isn’t? You could try a wildcard search like “mcs*mem” to see if that brings it up.
One other possibility is if you have a role and a privilege with the same name, that appears to get hidden during filtering. The fix for that issue should be in the 3.69.0 release.