One keyword gone in Google SERPs - Fred?

[head_dunce]

I have an ecommerce site. One keyword, which I use to rank #1 for on Google years ago, I'm now completely gone from the SERP's as of a couple weeks ago. I'm scratching my head here, my other keywords don't seem to have changed much recently.

Around mid-March of this year, which seems to line up with the Fred update, I noticed I went from page 3 to middle of page 1 for a few days with this keyword. It was a very happy few days. Then it slipped down and down and hovered around page 6. But as of a couple weeks ago, it's now gone.

Before the Fred update, I changed a bunch of product pages within the keyword category that had duplicate content because they were kits of items arranged different ways. So instead of repeating the individual item descriptions over and over in the different kits, I changed the descriptions on the kits to links to the individual items within the kits.

After the Fred update, at the end of March, I set all these kit item pages that I reduced to very thin content with just links to noindex.

My theory is that the Fred update reset algorithmic penalties for a couple days as it was being introduced. So the penalty of duplicate content that I may have had was lifted since I took out the duplicate content, and I made it back to page one. Then as Fred saw I now had a new penalty of thin content, I got hit and slid back down the rankings.

Now that I updated the pages that had very thin content to be noindex, do you think I'll see a return of the keyword to a higher position? Or any other theories or suggestions? I remember seeing keywords disappear and come back stronger years ago, but haven't seen anything like this in a long time.