Testing for a Thrown Entity

So I have come across some troubles lately. I was trying to come up with a command to find an item that a player throws on the ground, however it is slightly more complicated because it is a yellow stained glass pane (the trouble I am having is that I cannot get it to detect the colour yellow).

The current command I am using to test for the stained glass pane is this:

/testfor @e[type=Item] {Item:{id:minecraft:stained_glass_pane,Damage:4}}

I ran the command (in a repeating command block) and get no error response, but when I throw the yellow stained glass pane onto the ground, the command block doesn't react or give an output signal. If I remove the ,Damage:4 portion of the command, the command block will give an output if any glass pane is thrown.