why? like when your friend is not even online and not on mobile either then why this freaking sidebar shows them there ? sometimes they appear then disappear and again reappear, what that implies 
Same thing happens with me on my phone. I also need help.
Re: fb chat friends appear/disapper/reappear in the sidebar
This is maya.
What is, sometimes is. Sometimes isn't.
What isn't, sometimes isn't. Sometimes is.