Contact Pixel Support. They can move the stone.
On your game screen, choose the Settings wheel in the upper corner. Write down your Player ID and then choose the Support button.
Do not use the white text box in the center of the screen.
Choose a category at the bottom of the page. Then provide your Player ID, Web-based game vs. Mobile, and problem details.
If you do not see the category options on the SUPPORT page, you'll need to email PIXEL Support at: email@example.com . Be sure to include your Player ID.
Pixel Support responds by email. You may need to check your spam folder for their response. Support does not usually respond on Saturday or Sunday.