The car was running perfecty but suddenly died.

If no fault codes were stored, then what ever caused it to die, the ECM (engine computer) was not able to detect the fault. That means whatever
failed, the ECM does not monitor.

If for instance the ECM loses power, just like when you turn the key off, then the ECM does not store a code.

It could therefor be an Ignition Switch issue or a Power Supply Relay (for the ECM) issue. However, most vehicle these days, monitor power supply
to the Control Units and will set a "Battery B+ power too low" code.

Electrical gremlins can be a pain to fix, especially when they don't happen often enough. The fault needs to occur in order to find the cause.

Thomas

One thing to keep in mind when you have an issue like this and are under warranty is to complain about it a lot, call Volkswagon corporate office customer service and have the problem documented and if it is not resolved before warranty runs out call them again and be very pushy about the issue. Also ask the service department at the dealership to let you see all the, "Service Bulletins" on the car. These are internal documents that do not have to be distributed to owners like Recalls as they do not pose a safety hazard. Mechanics use them for diagnostics. But, you can use them to see if there are any related issues to your problem and use that bulletin to further document your problem anduse it to complain that it is an intermitant issue. The big problem with intermitant issues is getting the mechanic at the dealership to replicate the problem so it can be fixed. Also, it may not completly fail until the warranty runs out. This is where complaioning to the dealership and having your complaints documentd at the dealership and Volkswagon headquarters or customer service and finding any pertinant Service Bulletins will help you out. You can get repairs done after the warranty expires if it is well documented, complained enough times that it is a recurring problem and /or having a service bulletin on the issue will be the best information to have.
I had an S-10 with anintermitant transmission noise that could never be replicated and starting making a constant noise after the warranty ran out. I had plenty of complaionts documented, took it to several dealerships to have it looked at and called customer service to complain and have it documented several times. I kept all the apper work and I got the entire transmission replaced for free. I was not too far out of warranty so that helped.
So, make sure you do this to help your problem in the future if it persists and does not get fixed before the warranty expires.