My current active household consists of a married couple (both Sims I created), a Plumbot, a cat, and a horse.
I was setting up the couple to attend University together, and thought the neighborhood looked sort of odd when they arrived - it didn't look a thing like the University campus. I thought it a bit strange, but didn't pay it any mind, and the map still prompted me to select a place of residence for them, so I picked a place and got to work. I paused the game as soon as my Sims moved in so I could change the house a little and replace all the junky preset furniture. I spent about 2 hours entirely engrossed with fixing the place up, then when I went to resume the game by checking my Sims' class schedules, I realized that they didn't have class schedules at all, but their career menus, instead.
Upon zooming out to the overworld map, I found that my Sims hadn't gone to University at all: they'd merely moved to another lot within the same neighborhood with only the two of them, and that their original house was now for sale. Furthermore, the Plumbot, cat, and horse weren't there, either.
Luckily, I'd made a save not long before I decided to send them off to University, so I exited to the main menu in hopes of salvaging the situation. There, I found 3 saves: the first save was the save I made after fixing up their "rented" house, the second was a save that featured a blank family thumbnail, and the third was the save previously mentioned, where I'd saved before sending them off.
Now, here's where I REALLY screwed up: I decided to delete that second save.
Upon loading the third save, I found myself with the green box glitch - that is, my Sims' portraits wouldn't display, and even though my Sims were still present, I couldn't interact with them.
So, I logged out to the main menu again and decided to load up the first save, hoping that even if the old version was corrupted, at least I could salvage something from the new one, somehow. Their portrait boxes didn't even exist.
Pretty much frightened witless at this point, I quit the game entirely without saving and rush into my game files, hoping for some sort of backup I could resort to. Upon checking my SavedSims folder, I found that my Sims' files no longer exist.
I believe I may have accidentally deleted my Sims' .sims files by deleting that second save, somehow, and now I can't get them back. I've tried the Edit Town>Bulldoze>Copy method, but when I go to place a copy of them in the town, all of the lot markers disappear. I've also attempted the Split Household trick, as well, but to no success. I've even tried to export and then re-install them like a mod.
At this point, I feel sort of resigned to starting over (which is a huge bummer considering how very far I'd gotten), but I'd like to know if anyone else has seen or heard of this issue happening before, or if there might be any alternative measures I could try to maybe attempt getting my Sims back.