Missing Golden Gnome is Claimed but Does not Show on the Bookshelf

So I have seen the image that was built to tell you where each Gnome is located on the bookshelf. The one that I seem to be missing is the one found in the first bookshelf closest to the entrance on the right-hand side. The center shelf is blank. Looking at the image looks like the missing Gnome is located in Lunar Landing. From all of the guides, I have seen everyone claims there are only two Gnomes located on this level. (The one on the mining drill cockpit and the one in the hidden room after you push the button)

I saw some people claim there was a glitch in the game and that sometimes you have to play the level in Private vs. Multiplayer and then I found some people claim that they first collected the Gnomes as Plants and when they came back and collected them as Zombies it worked for them. I am not having any luck. Every time I go to collect it, it claims it has already been collected. I tried it with both Plants and Zombies in both the Multiplayer Arena and in Multi-Play. I was also hoping that maybe even though they claimed it was already collected that the bookshelf would magically show it. No luck.

I am stuck... any assistance/advice would be appreciated, my son and I are looking forward to getting all of the Gnomes.