Starter/ alternator connection in 1984 DL wagon
 

I had a starter fail recently and took the car to my newish mechanic, who replaced it. But when it was on the road a couple of weeks later the electrical failed. I was far from home and had it towed to a really nice garage that performed a complete inspection and determined " main power" wire was "broken." It looks more to me like "disconnected." Could that have been caused during the installation of the new starter? Here's a photo of the dangling cable. It was a simple repair but required a tow and a rental car, so if my mechanic is responsible, I'd like to know.
https://cimg5.ibsrv.net/gimg/volvofo...52c7002b18.png
Loose cable to alternator. From Starter?

That looks like the B+ cable behind the alternator. Supposed to be attached under the 13mm nut. Was the nut missing and the wire not attached to the alternator ( where someone left it loose the last time the alternator was replaced) or the wire was broken at the crimped on connector? Either way the starter is under the intake manifold on the other side of the engine and there would have been no reason to remove that nut when replacing a starter.

Did you not have an alternator warning lamp come on?

I was not actually with the car, hoonk, but your reply told me what I needed to know. I guess it was just a coincidence then. That alternator has been installed for at least 30 years, I believe. That's the last time I can remember having one installed.

Thank you!

If that alternator has not been touched in 30 years you should replace the alternator brush assembly soon or have another tow.