The loose ball play ended with the play, an incomplete pass. Remember, too, that a loose ball play has to occur behind the LOS...a fumble behind the LOS is a loose ball play...a fumble beyond the LOS is the end of a running play, of which you can have several.
The basic spot for a loose ball play is the previous spot, BUT the enforcement spot could be behind that if the all-but-one applies. Example : QB throws an incomplete pass, while teammate is holding 10 yards behind LOS. Enforcement spot is spot of foul.