For several months I have been working on my typeface, Theory Serif. It has made great progress and I was gradually learning how to use FontLab.
Since about an hour I have been trying to solve a problem I created by accident. I don’t know how it happened, but I must have duplicated the glyph “o” and deleted the glyph “n” in the process. I fixed it by adding the “n” back, by opening a backup of my font file. However, the o is now double in the font mapping and while I can find it, I can no longer see it (as a duplicate) in the actual glyphs window. When I find and double click the letter, it jumps back to the main glyphs window, with no particular glyph selected.
I have been going back and forth, but I couldn’t find anything about this in the user manual, in forums or on Typophile. Right now I can no longer export the typeface as a font, it comes back with an OTF error, due to the double mapping with the same letter. How do I remove this letter, or how do I fix the “n” and “0” mapping issue?
Here is a screenshot of the find box showing the duplicate “o”:

To make this question clearer: I cannot see or select this glyph, it does not show up anywhere. I can find it in the mapping, but I cannot delete the duplicate instance.