If there is no way for you to get to a mall or department store to make your purchase away from adult supervision, then you are going to have to get creative. You might mention that you need to go to the restroom and then quickly head to buy the underwear.
If it would be out of character for you to start doing your own laundry, then handwash your thong with soap and water and let it air dry somewhere discreet in your room.
Set an alarm reminder on your phone, tablet, or computer to remind you if you think there’s a chance you’ll forget.
