Really interesting point. I guess we don't know. It does seem though, that REALLY narrows down the number of people who could have answered that phone. It's conceivable with a cell, you could be at a party with your phone on the table and someone would answer it to jack with the caller, or it could be in a lost and found, or who knows what.
With a landline, you're down to MUCH fewer people. Instead of as you say, it makes wider the population of who could have answered the phone, in my opinion, it narrows it down to a bare, bare minimum. Like, her.
Good question.