Two months after someone threw a rock from an Interstate 5 overpass and caused a crash that injured two University of Oregon students, Oregon State Police got the break they needed to make an arrest. A Sutherlin High School teacher a week and a half ago overheard two students talking about an incriminating text message from Matthew Logan McKinney, 19, of Sutherlin, according to a police report filed in Douglas County Circuit Court. The teacher reported what he heard to Sutherlin police, who relayed the tip to state police. On Thursday, troopers interviewed and then arrested McKinney on suspicion of …