How do I get my desktop Icons back on my primary display?

I fixed this in in Display settings (System Settings --> Display). The three monitors I use are different sizes, but after dragging the monitors so that they were aligned along the bottom axis, my icons returned my primary monitor on the left

Like this

I am running Gnome and have a dual monitor setup. If I hit Alt+Space a menu pops up on my primary display and "Move to Monitor Right" or "Move to Monitor Left" is highlighted. Click that selection and the icons move to the other screen.

I wrote the iconic script to give control over which monitor icons are placed on. It also ensures icons don't get placed into the "black hole" that exists when monitors of different resolutions are used.

Here are a few screenshots of iconic to give you an idea of how it works.

iconic Monitors Notebook General Tab screenshot

On this notebook tab you can also specify the number of seconds a test will last. Press the Test button to place icons on the Desktop using currently defined each time you change the reserved screen space.

iconic Monitors Notebook Monitor 3 tab

Assign a user friendly name to each monitor. Set the number of rows and columns to utilize for icon placement on each monitor.

Use the Test button to view what icon placement after number or columns and/or rows are changed.