I'm personally more and more convinced that something happened to Karen in her own home, and that there was a sloppy job of trying to cover it up.
I think the reason police are desperately trying to reach out to deer hunters, etc. is possibly because perhaps her car was seen facing two different directions by different witnesses. Marty Lamb was a neighbor of the Swifts, drove to work early Sunday morning. If he pulled up behind her car and flashed her, as described in the media reports, then her car would have been on the west side of the road, facing south (unless he also made a U-turn, but that hasn't been reported). After Marty drove to work, I think Karen's car was moved to the other side of the road, then air was let out of her tire to make it appear as if she had a flat on her way home. Perhaps during the period when Marty drove up behind the car, that's when the perp was planting Karen's clothing (to make it appear as if Karen was sexually assaulted.)
Also, did it say somewhere that the daughter was "moved" to a different room at some point during the night? If so - something fishy was happening in their home.