Yes. Being a huge fan of Occam's razor, I agree, and think a kidnapper calling MW is actually MUCH simpler than the Irwins doing it.
Kidnapper calling MW:
Kidnapper walks in unlocked door, picks up baby and cell phones, calls MW for some kind of help and somehow someone else answers the phone. After a brief conversation, kidnapper hangs up.
Irwins calling MW:
They've killed their baby and are in the middle of hiding the evidence. One part of hiding the evidence is to get rid of the 3 cell phones on the table, which are active but they intend to lie and say they aren't active, because they want to make it appear that a kidnapper took the phones to keep them from being in communication with 911 when they discover the baby is missing. But to add a real confusing twist, they call a random number to totally confuse everyone as to whether the phones worked or not - in fact, they want to appear to be lying that the phones don't work, and cast doubt about if they were up making calls instead of sleeping innocently. So anyway back to the story. They randomly call someone who by the strangest coincidence DOES have ties to the area through her ex boyfriend. So someone picks up, and they decide to speak to the person, risking the person being able to recall the conversation and the voice. But that's all part of their diabolical plot, see, and it worked in their favor because no one can figure out who answered that random phone.
See how much simpler the first scene is?