Good job on being patient and not giving up. Funny what works sometimes. I had a similar experience just the other night; I was in deep water of about 25' and had my line hanging off the back of the boat from one pole while I changed baits on the other lines. Maybe a foot deep. I caught the movement of the tip of the rod out of the corner of my eye and a big bluegill had inhaled that lure and was just sitting there with it.
But now you've just added a new wrinkle in your brain for your future crappie catching and I'll bet your next one comes quicker on the next trip. If you have a 1/32 oz. Roadrunner in your arsenal, thread on a small plastic and toss and retrieve that in that same depth of water and see if you don't get a few strikes. That Beetlespin is also good for that; I should use it more but the RR has been working for me.