RD,
If we entertain the idea that the phones were turned off or batteries removed on Monday night , would it not be reasonable to think that someone had gained entry into her apartment and did whatever they did there and then take her from her home sometime during the night? Since we are speculating along these lines, could the responsible party in Jennifers abduction/disappearance have perhaps returned to her apartment after disposing of her to clean up and then perhaps go to work?
That's what I would expect to be a widely held view if have to deal with cell phones powered off at 10:40 pm.
But imo I would not think there is much possibility of this.
The assailant would have to check her belongings for any cell phones, gather them together, and power them off at same time. This could only be as a basis for taking them with Jennifer, all planned ahead.
The assailant would at some point remove Jennifer and items that she would normally take with her as in staging a disappearance. The friend's cell phone left behind would presumably be in one of those items, found, powered off at same time as her cell phone, and returned to the items taken with her.
Her cell phone would have to switch to another tower and back even though it's not moving in a car, to give some basis for the "can't be in two places at once" comment. This would be unusual to happen at this time sitting in her condo.
All of this would have to take place with no visible disturbance (e.g. nothing broken) having taken place during the abduction.
That's a very planned, very professional disappearance job. I suppose it's possible. But we have to set up this professional disappearance job meant to portray Jennifer as she would appear going to work because for no basis at all her loved ones don't believe she would take the phone anywhere for any reason after she hung up with Rob.
All indications are she did go out and drive a short distance to take the phone somewhere.