Mateusz "Matt" Rybarski, 21, who lives in unincorporated DuPage County near Addison, was last seen at home on Monday. His car and his backpack were found near Salt Creek outside Addison on Thursday, according to police and family friends. Rybarski, a gymnast, is in his last year of college, pursuing a bioengineering degree, but has been battling depression, according to a family friend.