I'm going to try to rephrase this in English and then give my answer:
There was a runner on 1st base (we'll call him R1) and the batter (B1) hit a ball to deep left center. R1 rounded 3rd base in an attempt to score. B1 went to 3rd thinking R1 was going to run home. R1 changed his mind and went back to 3rd base. B1 therefore went back to 2nd base.
Is that what you were trying to say?
Unless B1 ran past R1, there is no automatic out. If B1 also rounded 3rd and didn't retouch 3rd on the way back to 2nd he would be in jeopardy.
On a side note: Peck, you REALLY need to learn how to write. That might be the worst description of a play I've ever read.