By buddy just blew a transmission line somewhere up near the housing. It wouldn't even hold enough fluide to drive 500 feet.

He's got a 1999 4Runner Limited. Any advice folks? Is it possible for the line to just come loose?

 

I haven't heard of that happening before, but that doesn't mean it couldn't happen. It might be fatigue from flexing. If the motor or transmission mounts are bad it will flex a lot more. Don't drive it, tow it.