What was the story behind it? Was there a negative communication with the buyer? Any revisions?
I know it is not possible for us all to do revisions, and some buyers simply cannot be pleased, but I always include this tone when I deliver my orders to please let me know if there are problems, etc so we could possibly address it before leaving a poor review!
1 poor review is not the end of the world! I am sure you will receive many more high reviews!