This is weird enough that I don't expect to receive an answer.
I have a desktop PC (Win 8.1) that I use for all my development work. Fiddler is installed on this machine. I also have a MacBook Pro (Yosemite). When I want to work remotely, I use Microsoft Remote Desktop to log into my Windows box.
Fiddler works just fine as it always has on the desktop machine. But when I access the desktop machine via RDP from the Mac, the Response panel is gone from the Inspectors. I can see all the sessions on the left, but the right side only has the top right Request panel and all its tabs. The lower right Response panel is just plain gone, and no amount of resizing/minimizing/maximizing the window or closing/reopening the application makes it appear.
I can access the response by right clicking the session and choosing "Inspect in New Window" and pressing the Response button. So it's no show stopper. But it's... weird!