They are the ones who brought up the fact that the cellphones were gone. They made the cellphones a big deal. I don't think LE would have said to them, "Where are your cellphones."
There is "guilt" involving those cell phones, IMO. Maybe one or the other of them found some photo(s) that were of someone else, and that started some kind of an argument. Maybe it led to someone hurting the baby in a fit of rage. MOO
A lot of folks think that the baby was in the bedroom where the window is in the front of the house. Not so, it was in the middle of the house, according to the floorplan we have seen.
Therefore, an abductor, would have to go in that window, go to the middle bedroom, which was Baby Lisa's, between mom and dad's room and the boys room. That would take some real quiet behavior, and the perp could never be sure someone would not awake...
Then...stop and take the phones, with the baby????? Too risky, don't believe it.
Something on those phones that is not good..I think it is a photo(s)