A 24-hour social media vigil began at 6 p.m. Sunday. Participants are being asked to change their online social profile pictures to one of Sierra for a full day.
The search for the 15-year old continued this weekend with more than 500 volunteers looking for her and posting flyers.
Searchers focused on a 20 mile-radius around Sierra's home.
Sierra was last seen leaving for the school bus stop on March 16. Her purse, some clothes and her phone were found near her home.
No new clues were uncovered over the weekend.
Another search for her is scheduled for next Saturday.