Curt, they should be able to locate with the PIN and IMEI numbers, but again, like John said, it depends on who you talk to at AT&T. Getting the phone number from the SIM should be easy and will certainly locate the owner, if you are willing to do it.
I'm a long way from Exeter NH, but I have been there several times, and on Rte 111. Beautiful historic area. I have family from that area.