Battery and alternator issues

Three weeks ago my wife's car had a drained forty month old AAA battery (seventy two month warranty) after a couple days of real cold weather. No previous issues. Jump started fine but would not charge up after running for over thirty minutes. Had to jump one more time that day and again two days later to take it to a shop. Took to an auto electronic shop and they immediately checked it and said alternator was fine, but battery was drained and they offered to replace battery but found out mine was a AAA so I told them I would go to AAA to see if I could get it prorated. Went direct to AAA and they took it right into their shop and said that to be able to prorate the battery they would have to go through AAA's specific procedure which might take a couple hours. I got a call several hours later saying the battery was dead and they could prorate it and give me a new one and have it ready shortly. I gave them the go ahead and an hour later when I went to pick the car up was told there were the following problems after they put in the new battery: would not start; instrument cluster would not work; burning electrical odor and smoke from dash area; two fuses blown. They advised that they were trying to isolate the problem but that it might take a while. Two weeks later they call and tell me that they discovered that the alternator was the problem from the get go, that it was putting out over eighteen volts, and that the instrument cluster and restraint (airbag) control module were ruined because of it, and that the two fuses that kept blowing controlled those two items. What went wrong here? (Two to three years ago I had the alternator replaced with a new unit from an auto parts store).

The auto electronic shop owner said that he would have most definitely told me if the alternator output was abnormal!

The AAA shop did not check the alternator as part of their required procedure for prorating a battery.

What would have been the indications, if any, while I was driving if the alternator was putting out 18.5 volts before I got to the AAA shop? Could the alternator voltage regulator have failed just sitting there in their shop while AAA tried to externally charge the battery for their tests?

I did not have any smells, instrument cluster and lights were fine prior to and during the time I started and drove this vehicle before it went into the shop.

Alternator(reman), instrument cluster(salvage), control module(salvage) were replaced even though I had not given the go ahead.