How did the intruder know there wasn't an landline in the home? Just a thought. JMHO
IMHO...frame of reference. It may never have occurred to the perp to check for a land line.
The phones were there, and it was an opportunity to grab them.
I think the perp is a younger person. Anyone under 30 would think of cell phones first as being the only phones because that's how they live. Most of them would never think about a land line. I know of very few people who still have land lines, especially in that age group.
I also believe the person who took the baby is familiar with the family in some way.