If you think this, do you think he took Elizabeth because she recognized him? If so, this would seem to indicate to me he must have killed her. If she didn't recognize him, I would think he would have just left her when he drove off in his car. To kill her in this case would be particularly hard core.
I tend to believe she was taken by someone who intended to kidnap her but had the identical MO to Ricci and wanted to see what else he could get while he was in there, thus peaking in the brothers' bedroom when he was taking Elizabeth out of the house. Which means to me he was a low life loser, what of any possible value would anyone expect to find in young boys bedrooms, let alone be of enough value to take that kind of risk while holding a gun on the boys' sister while he was looking in there?