I have caught a lot of Crappie with a jig under a bobber, I usually use the weighted bobber (smallest that will float your jig and not sink) and usually I prefer a bobber as close to Sky color so it blends in and doesnt spook the fish, usually I have to use the brightyellow. I wish they would make weighted bobbers white on the bottom and bright orange on the top. Crappie generally feed "Up" so it's best to start high(6" under the bobber and work your way down until you get a strike. It is possible the crappie he caught were on the bed and he cleared them out. Try to find similar structure at a different location. I feel that the tube jigs under a bobber work a little better than a twist tail. Don't get frustrated, enjoy the challenge. My Grandma used to always say I wasn't holding my mouth right, when she was catching em and I wasn't. Good Luck!