Timing Chain Warranty

The chances of a timing chain going bad because you missed one oil change is about the dumbest think I heard of. THe only thing that may have caused it is if the oil was so low it wasn't lubericating the chain.

Is the engine still running? Is it making any noise? If the engine runs, the timing chaine isn't broken.

Let me know.

18,000 mile's on a oil change is a long time and could very well do in your timing chain. There different service interval's for different driving condition's. Like severe you would change your oil every 3750 mile's. Here is severe driving defined see if you fall into that interval.
SEVERE SERVICE
Follow the Severe Service Schedule if your driving habits frequently include one or more of the following driving conditions:

* Repeated short trips of less than 5 miles (8 km).
* Repeated short trips of less than 10 miles (16 km) with outside temperatures remaining below freezing.
* Operating in hot weather in stop-and-go "rush hour" traffic.
* Extensive idling and/or low speed driving for long distances, such as police, taxi or door-to-door delivery use.
* Driving in dusty conditions.
* Driving on rough, muddy, or salt spread roads.
* Towing a trailer, using a camper or a car-top carrier.

To tell you the truth, I'm shock the timing chain is the only thing shot. That is the fastest way to ruin a motor known to man. I actually think 7500 miles is too far between oil changes but 18K will ruin any motor.