"There is nothing you can do, Ron. They go somewhere kill someone and go back to their hide-out. You can't do anything unless you catch them during a battle," Draco pointed out. "Anything else is a waste of time and a risk, and you don't want that." This was probably the reason why Gryffindors seemed to solve the impossible: they try or die. Slytherins just waited for the right moment.
"Look, don't think they were connected, but I will get you what you want, when I find out." He grinned. "You know there are plenty of Order members in the Aurors. You could try them, too, although if they really think Miles did it, they must be insane."