[Pontiac]

His cell phone and credit cards had been used after he disappeared.

Someone would have to exceptionally stupid to use the cell phone of a missing (murdered) person.

All cell phone companies record the number called. Almost all cell phone companies can now triangulate to locate an active cell phone.

All the police need to do is find the persons called from the cell phone and question the people called to find their suspect.

If that is not successful wait for the cell phone to be turned on and track down the suspect.

[El Gran Salseron]

In response to your post # 8:

Yes, I am aware of that and you are aware of that but dumb criminals are not. :-)

Hmm.....isn't "dumb criminal" a redundancy?