Would US LE even be able to enter Mexico to do that? They would have to have evidence she was taken to Mexico by her dad to justify watching him and I'm not sure the Mexican govt would allow American LE in to do it. It sounds like the Mexican authorities promised to look into it but never did--whether there was a miscommunication or another reason they never questioned the dad is up to interpretation. Unfortunately, they don't even have evidence Diana left the state of Florida.

I want to believe she is safe somewhere but I'm being realistic--there would be some more evidence pointing to Mexico or some tips saying they were seen crossing the border, IMO. That creep they arrested needs to talk and tell where he took Diana.