Probably a Sarcophagidae, a group of flies which give birth to live young. Eggs hatch inside, etc.
Sarcophagidae (grey striped flesh fly) is exactly what it was. I didn't know any flys gave birth to live larva but that fits with the particulars of this case... it was after my chicken sandwich to convert it into a playroom for it's baby creepy crawlers! Thanks for the info.
