Gina, sorry to hear about your experience.
First, don't take it to the dealer, I question how he came to his conclusion.
We will try to help you decipher what might have went wrong by reading about your experience from our PC's. This is difficult to do and an actual tare down of the engine would be the proper way to go.
But so that we can begin to help you, a good recollection of what you experienced soon after the repair and what you felt and heard at the moments before and after it died may help.
Many of us on this forum know more about this vehicle than most techs and may be able to assist you from afar, so let's see.
Also, can you give us more details about what your mechanic did to perform the work? His response would most helpful. How did he perform the timing belt replacement procedure, what procedure did he follow?
How did the dealer come to his conclusion? Did the tech turn the engine using a wrench and then discover that it didn't move, the engine was frozen?
When you said that the CRD "will not now start", did the engine not turn over (rotate) when you turned the ignition key..... did you hear the engine crank over?
I love my CRD too, and I hate to hear about mishaps like this. It's such a great vehicle when it functions and is repaired properly.
I send you my best wishes for a smooth and economical recovery.
Racer.