OK, panic setting in. Do you think I racked off too much yeast if I sucked it up from the bottom? I thought it looked like they were in suspension but my gallon jug seems to be fermenting. I think I'll decant and put back the trub.....
Once you pitched, and the yeast started multiplying, the yeast are everywhere. When you pulled the trub and beer from the bottom, you most definitely got yeast in there, hence the fermentation. There should be no issues, and your beer in the carboy should be fermenting as well on its own. I would let it ferment itself out, and then decant it back into the beer when you rack to secondary or a keg. It should be clean as long as you used good sanitation.
I plan to decant off the wort and use as my next starter.
Hadn't you already pitched the yeast?
When I read this first, I thought you were planning on using that as a starter of whatever yeast you originally used. But if you weren't, you aren't going to be able to use that for a starter, because as Sean said, its going to ferment because you already pitched the yeast.