Safetymom........I obviously do not know what steps Law Enforcement has taken so far, but this might be a suggestion if they haven't tried it:
Cell phone tracking service
An interesting thread on Google Answers, regarding what services are available to track the current location of a cell phone.
For about $200.00 ICU, Inc. offers to locate a cellular telephone by
pinging the phone a kind of triangulation process similar to the one
I mentioned earlier. Ms. Landers explained that the cell phone appears
as a blip on a screen. They provide the service 24 hours a day, 7
days a week in order to help locate missing persons, fugitives,
cheating spouses, etc. They regularly serve bondsmen, authorities,
investigators and many others. You will receive the results within 7
to 10 minutes of a successfully completed ping that will indicate
within approximately 50 feet, where the phone was located at the time
of the ping.
I.C.U. Inc.
http://www.tracerservices.com/cpl.htm
http://www.tracerservices.com/cplfaqs.htm
FIND OUT IF THEY "PINGED" HIS CELL PHONE.
Sending Prayers..........Jim