That

[greymule]

I would allow the runner 1B in the situation you describe. As long as he's sort of standing around, he's OK to go to 1B. Now does putting on his glove constitute abandonment? Hmmm . . .

You would have to watch carefully if there were, say, a runner on 3B, because that runner could also abandon effort or be tagged out or who knows what.

Now if the teams changed sides and the batter who struck out on the dropped third strike was standing in left field as his pitcher was warming up, I'd say that was too late to go to 1B. By clearly going to field his position, the BR had abandoned effort.

Maybe another poster can cite the exact point at which the BR can no longer go to 1B.