After the first bid, West says that he heard something from the other table as they finished the boards and passed it to this table. The TD is not called and West does not say what he heard.
1. If the TD is called and finds that West heard "We should have bid six hearts", how do you rule?
When the auction reaches 6♠ P P, the TD is called. South wants to know whether what West heard has affected his 6♠ bid.
2. What should the TD rule now?
As the TD, I decided that the damage had been done and instructed play to continue. I did not find out what West had heard and I did not answer South's question. I checked the other table in the match and they had already played the board.
South doubled and East took the club finesse for 6♠X=. I now asked West what he had heard. The result at the other table was 6♥-1 by South.
3. Do you adjust the score at this table/match?
I decided that had I been called at 1♦ I would have found that West hearing "We should have bid six hearts" could interfere with normal play and awarded an artificial adjusted score +3IMP to both sides.
I know some contributors to this forum would have ruled differently, because they told me so at the event.

Help

W . N . E . S
. . 1♦ 1♠ 2♥
4♠ 5♥ 5♠ 6♥
6♠ P . P . X
P . P . P