I think, the transaction in credit card on Monday and the voice mail checked after two days later should give the solid lead in this case. Generally the credit card company should be able to put red flag by checking the signature and the type of the store it was used in, if the credit card is indeed stolen. Again, Denver international airport is quite a distance from the Estes park and Denver downtown. The person who used the cell phone either has to rent a car in the airport or flying through the airliners, my guess. They know exact time, they should be able to look in the camera round the airport at that time. I think those two are the leads police should be looking. Just my opinion.