Just download/open the torrent again, and when the torrent app opens the window asking where to save it, point it at the folder where your last downlaod was going, it will see it and do a check, see what has been completed, what is still missing, and pick up where it left off.
Remember this, the only stupid question is the one you don't ask.
"The thing about changing the world... is that once you do it, the world's all different."
Let's share our knowledge. Otherwise, what's the point?