Player shown offline but is in game with me and can chat with me (not mobile ap)

So, a friend of min is randomly being shown as offline even when we're in a lobby together or chatting. Sometimes after we finish a game he will appear. It's only true for one firend and several of us are unable to see him online. Has anyone come across this before?

P.S. If LoL finally has an incognito mode....... HOW DO I USE IT???!!!