A picture is worth a thousand words (especially when you write on it):

That's the Sim City I've been playing since I started S,HWC, which is attached to my Strangetown. There are missing lots all over the place. I've already dealt with this in Pleasantview, with Dina and her kids going missing from their home lot, which, oddly enough, was still there (and I eventually found them in the townie menu of InSim's Summoner, which was rather odd). Today I noticed that the fraternity at La Fiesta Tech is missing, and now Sim City is missing a LOT of lots. Not to flail dramatically, but I do believe the end may be nigh for these aged neighborhoods.
I found
a thread at MATY that mentions something similar to this, and Pescado said, "In order to retrieve such a missing lot, you need to extract the lot entry from a backup neighborhood where it still exists, and import that entry into your neighborhood. This is a nonstandard SimPE operation and should restore the missing lot from limbo. If you don't know how to perform this, well, then, you're SOL." Great. Does anyone out there know anything about this particular operation?
Even if I figured out how to restore them, I think it'll just continue to happen. Perhaps it's time for me to consider a mass exodus of sims and lots and start over in a merged hood.