Just got my bike back from LBS with new shifter cables put in. When I got it home my Ultegra R8000 front der indexing is off and the barrel won't get it there, so I decided to tighten the cable.

I loosened the cable tightening bolt and it looked frayed. Could it possibly be frayed already just from its initial installation? (I haven't even ridden it yet). Or could the LBS have somehow "forgotten" to put the new cable in?

Even weirder, now the tightening bolt won't tighten. It just keeps spinning. I don't understand how I could have stripped it just by loosening it. And it was tight enough to shift before I started working on it. Could I have disengaged it from an underlying mounting nut somehow that now I'll have to fish out to re-engage the bolt?

Sorry the picture isn't better—this is the best I could get after 20 minutes of trying, and I have to get to bed for a race in the morning (guess I'll be racing my training bike). Many thanks for any advice!