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What were the symptoms? Any part can fail suddenly but there is usually some kind of warning or observations.

Why did you take it to the shop? What was the symptom?

I did read about something that would cause a sudden failure like that but I can't remember what it was. If you have a computer-controlled transmission, there will be electrical tests they can do after connecting a hand-held computer called a scanner. If it is the older style hydraulically-controlled transmission, there are a number of test ports on it where they can take readings to verify what is not working. Although not common, a plugged filter can cause a failure to move. Even just low fluid level can cause that too but that will usually give a little warning in the form of slipping or moving sluggishly first. If you have a reputable transmission specialty shop nearby, you might consider calling them for a second opinion although there is no way they can say for sure what's wrong without seeing the vehicle. They would likely know of any common problems and what it will take to fix it. Be aware that some transmission shops will just want to replace the transmission or rebuild yours because that is what they do on a regular basis and can do the fastest. Regular repair shops will typically diagnose the problem and repair just that. The diagnosis will take longer which will cost more but the repairs can cost less.

Holler back with what they find so I can put it in my memory banks.