I would worry about 2 things:
- that the temp wouldn't get high enough to get rid of bacteria. If you are at home, I would put it in a regular pot, and bring it to high heat fast (you'll have to stir often to keep it from sticking), or turn your slow cooker to high and give it several hours at high.
-if you have used regular ground beef you're going to have a lot of fat.
How to remedy this? (especially if you're gone for the day), freeze it. Use it a few days from now. The freezing will kill anything that may have come to life, plus the excess fat will freeze as a layer on the top and you can scrape it off before you reheat it. Besides, chili always tastes best the day or two or three after it was made!