Put yourself in Toni and Dallas shoes - you have just seen the taxi drive off with your passports and money. What would you have done?
It happens all the time that people leave things in taxis. With a bit of luck you know the name of the taxi company, and then you get on the phone and hope that dispatch can find the car and your bag. This is certainly much harder in a foreign language and the larger the city (and Moscow is not small).
At least in most Canadian and American cities (at least in my experience) the taxi companies are registered and print their company name on the vehicles. This didn't seem to be the case in many of the TAR countries.
Could Dallas have grabbed another taxi and said "follow that car!"??
It was certainly a tough situation. What would you have done??