Anyway to track down a lost iphone 3g?

so last week, i lost my iphone 3g, so im assuming someone took it, since they updated my Facebook status just now with my iphone on my account.. (i never logged out facebook on my iphone). but anyways, is there anyway i can track it down? its an iphone 3g, NOT jailbroken/unlocked. but i went to my phone company on the day i lost it, and they cancelled the sim card in my iphone, and gave me a new sim card with the same number (i use my old phone now), so in other words, i can't track my iphone down with my number. i dont want to call the cops, because its just an iphone 3g, and there's some problems with it, so the police isn't really going to take it seriously. and i have all my passwords saved in my 'notes' app.. my msn passwords, twitter, etc. and i didnt set a passcode lock on my iphone.. (i know, call me stupid :/ ). but my dad got that iphone for me for my birthday... and its probably the most expensive gift he's ever gotten me.. so it's really important and special to me.. any help please?