1997 Toyota 4Runner Repair shortcuts

Have you ever heard of Mechanics clamping off the rear brake line while doing work on the front brakes? I just took my 4Runner into a Toyota dealer and they found my rear brake line clamped off with a vice grip. They had to go up above the spare tire to find this "clamp" and it was placed on a short piece of flexible brake line between to rigid metal lines. They asked if I had any enemies? I asked why they might have done this, because I had no enemies and they were the last ones to work on the vehicle and they did brake work. I am thinking this was some kind of short cut one of their mechanics used and forgot to undo.

Any thoughts?

I can't believe anyone would have crawled under my vehicle and done this, much less known where to find the tube to clamp.