The pretty 16-year-old, known as "Mickey" to pals vanished walking home from West Wendover High School last Thursday.
But after a huge searched, including many community members, a volunteer found her body in a shallow grave in the Nevada Desert about five miles west of the town.
Police Chief Ron Supp said finding the body in such a remote landscape was fortunate adding: "Many of our staff has referred to it as divine intervention."
But while there are no concrete clues pointing to a suspect he said: "I
am relatively confident in our department and the rest of the people that are involved here that we will solve this case."
Micaela's distraught mother told ABC News: "This is not over yet until the person or persons responsible are brought to justice."
Friends, shocked by her death said Costanzo was a good student and was well-liked by her classmates.