Deleted photos sometimes show up in Family Tree as a person's portrait photo.
In Family Tree, each person can have a portrait photo. That portrait photo could have been uploaded by you or another user. If the user who contributed the portrait photo deletes it from FamilySearch, Family Tree still uses that deleted photo as the person's portrait.
If the portrait photo is removed or changed, it cannot be changed back to the deleted photo.
This works the same in the Family Tree web application and mobile apps.