It's a 1992 Plymouth Grand Voyager.

The car was doing fine and all of a sudden the charging system went down to zero. It would appear that the alternator just gave out with no warning. Now, here's the kicker: when I checked under the hood, the positive battery cable was loose. Not off, but loose enough that it might have been arcing. Could that have damaged the alternator while driving? I ask because the last person under there was a mechanic working on something else in that area, and if he loosened the cable and destroyed the alternator, I want to hold him responsible. But if this scenario couldn't happen, I don't want to accuse him unjustly. So, is it possible that's what killed the alternator?

That can often be enough to fry the regulator or diode packed in the alternator... the arcing causes power spikes and surges that will toast solid state devices. And it usually happens pretty quick... not weeks or months.

Now accusing and proving are two different things. There is always the chance it died on its own... especially if it has a lot of miles. THey don't last forever.

It's possible it burned out the regulator. Alternators also "go to zero," when the brushes wear down too far. Remove the alternator, check the length of the brushes and the regulator--not a hard job. You may be able to simply remove the back cover and replace the regulator/brush holder assembly, assuming no damage was done to the rectifier (which is usually the case).

For around $20, you can rebuild most alternators. It's a fun, easy project. The rebuilding procedure will be similar to that in the link below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-13.html#post2518522

I'd opt for this route.

So it's very likely that's what happened, and proving it is pretty well impossible. Grr.

Yes. It's not worth the effort, especially when you can likely fix it easily. Just disconnect the negative battery cable, remove the back of the alternator, and install a new regulator/brush holder (3 screws). You may not even need to remove the alternator from the vehicle. Besides, alternators usually last only 100,000 miles or so before they need rebuilding or replacing.