I lost my phone.. argh?

Or so I think!

So, I'm on vacation in North Carolina with my family and another family (who I don't really like in the first place.) Anyway, I went to sleep last night and had my phone plugged into the wall. I am positive of that.

This morning, it's not there. So, I overslept because it doubles as my alarm clock.

Anyway, I need to get my phone back from my sister and the girl from this other family (oh come on, did you really think I misplaced it?).

I would prefer to get this phone back quickly because:

1. I'm breaking up with my friend's boyfriend (lonnnnnnnnng story. But I'm straight and I don't want my sister taking it the wrong way.)

2. I need to talk to my friend.

3. I have some stuff on there that they can't see. (Such as plan arrangements, party information, gift ideas {because my sister's birthday is coming up} and a few text messages I don't want them to see.)

And when I do get/find my phone. How can I make sure it's not stolen again? Any ideas?