Source monitor timeline disappears

I've been working in Premiere intensively for over 5 years now on a variety of systems including mac and windows and never seen this and try and keep an eye on this forum on a regular basis and don't remember seeing other reports of this behavior.  Not doubting your experience, just trying to get a handle on what's going on.   Might be a good idea to tell us your system specs: OS version, Premiere version, amount of RAM, Hardware specs including graphics card. 

Have you tried resetting your workspaces?