I play fantasy baseball in a head-to-head league on Yahoo! I had a bunch of Tigers and White Sox starting yesterday, and the game got rained out. I’m guessing that if the game isn’t played that week, then I just don’t get any stats from those players. Is that true?

Yes that is true. No game..No stats. When the game is eventually made up is when the stats count. So if there is not a Double header or the game is not made up in the same scoring week you are out of luck.