Contamination with baker's yeast?
I've been monkeying around with firm starters, and haven't had a lot of success using a firm starter from start to loaf (I never get enough leavening power). The other day I figured I'd convert some of my sticky "levain" into a more liquid starter. Made up a batter, which started bubbling almost immediately. I'm pretty certain my levains had wild yeast, just not a LOT of it. Anyways, after a couple feedings my liquid buddy is growing nicely. However, this morning I fed it, and within 2 hours it had doubled, within 3 it had nearly tripled. This seems like a pretty short lag time, but I'm very new to wild yeasts.
So, a question in two parts: Can a new starter get contaminated with baker's yeast? (I bake a lot, I assume there's baker's yeast pretty much all over the place) How would I know if it had?