How to search your DNA matches for people with no user name

[kiterunner]

Just seen this on Facebook and thought I would post it on here for reference - somehow, some people can show up in your list of DNA matches with no name at all, and now you can search for them by putting "Null" in the Match Name search field. Nobody seems to know how they managed to have no user name in the first place but at least we can find them now.