I lost the whole desktop (except for one icon) in front of a class today after plugging an HDMI cable in, via a Moshi adapter.
I'm using a MacBook Pro 17 Mid-2011 with the latest Yosemite. I was running a 1920X1200 screen on a 1920X1080 projector
After resetting the PRAM, deleting some plists and making a few other stabs in the dark, I clicked on my desktop, which revealed the "Finder/File/Edit/View/Go/Window/Help" tabs, then I chose "View>Show View Options." I slid the "Icon Size" to the tiniest possible size, then I slid the "Grid Spacing" to the largest possible size and did a "Command+A to select all. I dragged my one Icon to the left and voila! Icons! All of those rascals were hiding just off the right side of my screen. I guess there's more than 1920, virtually speaking.