Biokleen (biodegradable detergent) soaked into drywall
Mold is already everywhere (how do you think it gets around so quickly?) and its danger is severely overblown for most people. Scrub with a mild detergent, dry things out well, and don't worry about it. Prime with a stain blocker and paint if you like. 

There's hardly a house on the planet without a little mold somewhere in it. A gallon of wet certainly didn't destroy your wall or put your health at additional risk. It's cases with massive amounts of moisture over a period of time that cause concern. 

Based on your description you may simply have concentrated cleaner collected on the wall and floor. Again, scrub it up with mild detergent.