Well :waitasec: he obviously had to have a way to get from point "A" where he left the Hummer to point "B".. :waitasec: wherever that was. Otherwise he would have been on foot and I'm not sure if DSSR's place is within walking distance of where the hummer was found or not.
Also, this may have already been discussed but is OnStar a feature on Hummers?
Answering my own question...
Found this:
2008 HUMMER H3 Features & Specs
Telematics
Hands free phone
OnStar telecommunications service
http://www.edmunds.com/hummer/h3/2008/features-specs.html