Sorry I'm late to the game, Plumbob95.
What you're experiencing is a known (and very annoying) bug in World Adventures. There's no way to actually fix the bug. The game does make a backup copy of the last save, but if that save was during the vacation, it will probably get the bug again. It's worth a try, though, if you haven't already.
Click here for instructions. Unfortunately, if the backup copy does the same thing, you're pretty much out of luck.
The best way to keep this from ruining your game in the future is to make multiple copies of your game when you save it. To do this, you use the Save As function and give it a name that's slightly different than the original name. For example, I name my files "Dreamweaver DecaDynasty 1.0" then Dreamweaver DecaDynasty 1.1" and so on. I normally keep about 4 copies of the game like that. If anything goes wrong, you can go back to a previous save and play it again. Also, be sure to always save
before your Sims leave for vacation. It's a great help when this travel bug strikes.