someone is sending emails via my lost iphone!

okay so a girl took a photo of her dog in one, and a photo of herself in the other email...
both of these email were discovered in my sent emails section on my gmail two days ago.. my phone has been missing for a few months now i've since purchased a 20 buck phone with a new sim card... so i'm not concerned with my phone line being misused..
she apparently emailed those photos to, i'm assuming, herself.. with the recipients email address viewable to me...
my question is should i try to contact this person and hope for a safe return of my iphone maybe a reward even....
or
is there anyway to trace the iphone some how hack into it could google help with this .... i don't know...
anyone with any information or suggestions please help...

ps my iphone is jailbroken and unlocked, no retrievable apps were installed, except for one navizon but i never activated it as it turns out... oh and i don't have mobile me
i'm going to upload the photo she took of herself as my profile picture not that it helps, just for those of you curious

Just change all your account passwords and the phone will be blocked from accessing your email or using your account. Aside from that you can retrieve your IMEI and/or serial # from a back up of your phone from the last sync in iTunes. Go to Edit > Preferences > Devices and hover your mouse over the backup to see serial and/or IMEI. I've been told that the police can use the IMEI (not sure about serial#) to track the phone using the on board GPS.. not sure if that will work but suppose it might be worth a try.. Good luck!