For anyone who comes here with this problem, but does not read the comments, you can get it back by hitting CMD-1 (as noted above), but it will only show for the full size emulation, if you want it zoomed out, it goes away.
then you have to use the shift-cmd-H to click the home button. And you can do it twice to simulate the click-click to show running apps, and then close them. (Don't press and hold tho, that will just trigger it to keep opening/closing the running apps window)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…