Hubby and I were just reminiscing about how difficult it really was getting past the borders when we visited one another. I had to prove I was going back to the States when I visited (letter from employer, return ticket, etc.) and it was even worse for my husband going into the US at Newark.
I can't help but feel Zahra fell through every crack along the way. Legally she shouldn't have been allowed to leave Oz without a court order according to the AFP website much less being moved half a world away. (And I think, on a personal note, AB gives loving parents who do LEGALLY move their children to a foreign country a bad rap. GRRR.) Someone speculated AB should have been more involved post-relocation and I couldn't agree more.
http://www.afp.gov.au/policing/family-law/family-law-kit.aspx
I feel your pain about the border crossings, my husband and I had the same experiences.