Fun Fact: dogs instinctively bury toys, chews, and bones because it used to be the only way to protect their belongings from other animals in the wild. Primal instincts, right?
A very long time ago when dog's were wild and roamed in packs, it was their job to find their own food - like every other animal. This wasn't always an easy task, often placing the pack under great physical stress and with inconsistent food sources. In order to ensure that what they found (carcasses/bones) would be kept in a safe place for future feedings, they would bury them deep into the dirt. By doing so, the dirt kept other animals from finding the remains of their food.
Instinctually - not because they are hungry as domesticated puppies - they feel the need to hide some of their favorite things or extra food (like treats) for later. This is especially true when it comes to a favorite bone.
If you are a busy pet parent and sometimes fall short of play time with your pup, you may find household items that you use on a daily basis go missing. Some dogs hide or bury shoes, tv remotes, and personal belongings as a way to beg for attention or play time. After all, our furry friends are all about game playing!