I had a very strange (and dangerous) experience with my 2007 Hyundai Sonata yesterday evening. I was pulling off of the highway onto an exit ramp. I started to press the brakes as I approached the stop sign. When I was almost at a complete stop, my car completely died. I did not notice it until I tried to accelerate and nothing happened. All of the lights were completely out, as was the engine, and the car was stuck in gear. Specifically, I could only change between drive and neutral and my keys were stuck in the ignition (they could not be turned or removed, despite trying to turn the steering wheel). I was almost rear-ended by the car behind me because they were not expecting the stop.

A friend just happened to see me (extreme coincidence) and he helped to push my car off of the exit and to the side of the road. As I was calling roadside assistance, I noticed I was able to put the car in park and I tried starting the car up - it worked just fine. There were no new lights indicating a problem on the dash.

I took it to a mechanic nearby. They have had it for almost a day for troubleshooting. They originally said that it was the alternator yesterday evening. But when I called to check on the status today, they said that they re-tested the alternator this morning and it was fine, so they did not order the part. They said there were no codes available to read from the system. I also called the dealership in town to see if this is a known issue, recall, or problem. The guy basically told me that unless they can replicate the issue or there is a code, that it will be a waste of my money because they won't know what to fix. I appreciated the honesty but I don't find these answers to be acceptable. My car literally DIED while I was driving! I am just grateful that it wasn't a more serious problem or an accident. I am going to be incredibly nervous to drive it again without knowing what the issue is or if it could happen again. I've looked up various threads and have seen a few suggestions but the symptoms don't seem the same as what I've experienced. My car isn't exactly new (~62,000 miles), but a little too "young", in my opinion, for something serious like this to be happening. Any suggestions?

As one last note, I should mention that the check Air Bag light came on earlier this week. But to me that seems entirely unrelated.
I also thought I had heard my car making a "squeaking" noise while I was driving the other day. I had my fiancé listen for it and he could barely hear it. But after driving a few times I swore it was there. It's extremely faint but a constant noise. When this happened to my car I had JUST been thinking about the squeaking noise I had heard (I did NOT hear it before my car "died") and how I needed to take my car in to get checked this weekend. May be unrelated but thought I should at least note it.

 

Maybe a look at this from another perspective.
When everything shuts down all at once and you get absolutely nothing on the dash or when attempting to start the vehicle that means you lost all power. That can be caused by a dirty battery cable connection , power supply or ground connection. It would not be an alt problem because the vehicle was able to start shortly afterward. And that would rule out the battery itself.
Do you know what the condition of the battery cable connections were when the first shop started working on it?

 

I did not check the battery connections before the shop started working on it. They could not find anything wrong so I picked the car up this morning.

I drove it to work and the entire way I heard a soft but constant high-pitched kind of "squeak" as I was driving.

 

Do you hear the high pitched squeal when the vehicle is running but not moving?
If so, then there could be anything from a dry belt, possible tensioner bearing getting ready to let go.
If you only hear it when the vehicle is moving then your shop will need to take it for a test drive with you so you can point it out to the gentleman. A lot of shops are pretty noisy and unless the squeal/squeek is loud they probably can't hear it.