Regarding the properties pane it's been a long time I haven't faced this issue. When this occured, I had some chance to get it back, sometime it would definitively not. I was used to detach the MM window from the dock then maximize it on the screen (either primary or secondary) and close vegas. Doing this way I was able to drag with the mouse in order to get it.
I believe that from time, MM records funny geometry which is being recalled for further sessions. Infortunately when it's really out of bounds you're out of luck and have to try several attach/detach/maximise/exit and vegas restart, with or without success.
It's one of the glitches MM has... IMHO, the worse is the blatant memory leak in the thumbnail chooser code. It gives you a straightforward way to crash Vegas in one minute. The "lethal" feature of MM SCS doesn't care about.