Just went through something like this myself. 4 week old imperial Porter (Denny conn) and decided to change my blowoff tube water (no sanitizer) due to the start of mold upon the surface. Had some liquid in the tube which got sucked back into th fermenter as I pulled it out. Like a dumb@ss I reinserted the tube back into the bucket in haste and then back out again as I started to panic...resulting in the additional liquid being sucked back into the fermenter. In total, I'd save about 1-2 oz of liquid. In terms of the mold, I'm not entirely sure. Managed to change the water and added sanitizer this time.
Should I transfer the beer tomorrow, leaving what mold may have been introduced or should there be sufficient alcohol (6-7%) to keep it from being a problem?