Well, me being a young angler, I might not have as much experience as some of the other members. Anyway, couldn't you fan cast with a crankbait allowing it run on the bottom, so it sent back a physical feeling of what you were bumping into? You could try to remember what kind of structure was there and where it was located on the lake or reservoir. I know you couldn't see the lure, but could this work? Correct me if i'm wrong please.
-DO