Looking for title of book...PLEASE HELP!!

[jucrunk7]

Okay hi guys, how are you all?
I have a big favor to ask. My mother is looking for a book that she read about thirty years ago as a kid.

It was about a family who went to florida for christmas. then the parents left on plane and flew home.
and the kids a brother and sister i think went with the grandmother or someone and drove home.
they decided to pick up two young about college aged guys who were hitch hiking. it turns out it was actually a guy and his gf. for some reason they thought if they were two guys they'd get picked up easier or something.
anyhow...after the family picked them up they actually took hostage or hi jacked the family.

the parent who flew home somhow knew about it...and when they found out they ended up putting some sort of sign on the car like a flag or something on the antenna to let them know that they were still with the bad people who kidnapped them.

anyhow. i never read the book and i'm not sure if this is exactly how it goes...but if anyone has ANY i mean ANY CLUE please let me know.
thank you
Mel

[neglet]

That description doesn't ring any bells. Have you tried googling key phrases, like "book summary" "kidnapping" "hostage" "teenagers" to see what happens? Good luck finding it--a 30 year old book, that's a tall order to identify.