I think I know what happened. When I posted the 2008 Lexicon I had to change some headings and add in some new entries above "Alpha Freeper". I'm betting I screwed up and, unknowingly, had "Alpha Freeper" selected when I hit the delete button and replaced the old text.
Phew. I have restored the entry on my profile page and will be more careful next time.
After further review, I lied. Apparently the entry was missing from when I “stepped in it” and started updating the lexicon (in 2006). IOW, I don’t know how I messed up and lost the entry. Thanks for restoring it.