Time-saving action steps for the seller here:
1. Post the PM, if there is one, showing the time stamp. Everyone's happy, this goes away. This is the only way at this point to clear your name.
2. PM with timestamp doesn't exist - just come out already, admit you sold for a higher price and take your lumps. Most readers assume this is the case anyways.
3. There is no option 3. Posting anything else is a waste of time.