Day, 25, was last seen on Aug. 24 entering a cannabis dispensary in Bloomington.
He was reported missing the next day by the chair of the Illinois State University speech pathology department.
Day's 2019 Chrysler was located on Aug. 26 in the woods south of the Peru, Illinois YMCA.
A body was found by searchers on Sept. 4 and DNA results are still pending.
His family is offering a $25,000 reward for information leading to him.