Very interesting indeed.
Here's what I noticed down at Lake Mattamuskeet:
Along one lock, I had two handlines and four traps in the water. On one particular handline I kept getting something. I'd pull the line in slowly only to have the crab drop off at the last second. As soon as I put the bait back in the water, the crab would start hitting it again (it wasn't a turtle). After several futile attempts to catch this crab, I pulled up the handline and threw in a trap in the exact same location. I was certain that the crab would go into the trap and I'd have him. After 4 or 5 pulls from the trap, nothing.

So, I pulled the trap and put back the handline. And wouldn't you know, that pesky crab was right back at it again. And he kept dropping off at the last minute like usual.
So, here's what I did:
I put a large unbaited ring-trap straight down from where I was standing. When the crab was back on my line, I slowly pulled him in. When he got over the ring trap, I pulled it up and nailed him!

But, your story explains why the first trap didn't catch him. Perhaps he was a cunning and smart crab and stayed clear of unknown objects.
