The mood meter, instead of green was blue and I could not see any of my sims
I've definitely never heard of a blue mood meter (would love to see a screenshot). But the missing Sims is probably one of the traveling bugs. There are no known solutions to the travel bugs and you mostly just have to rely on previous saves. If you didn't save while in China, you could exit the game without saving and then pick it back up before the trip. You really should get into the habit of backing up your game file. It's as simple as using "Save As" and giving the file a different name. For example, my DecaDynasty files are like this:
Dreamweaver Townie DecaDynasty 1.1
Dreamweaver Townie DecaDynasty 1.2
Dreamweaver Townie DecaDynasty 1.3
Dreamweaver Townie DecaDynasty 1.4
And so on. After awhile, I'll start using the names again or deleting the oldest of the files to free up some room on my computer and in my game.