Man, that stinks! Sorry that happened. Luckily nothing super major to fix if it's the alternator, right?

I had a very similar thing happen on my Mazda years ago; alternator seized. Pretty much without any warning. It snapped the serpentine belt, left me stranded without a working water pump, much like yours. New belt and alternator, was up and running soon after.

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"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)