We had something very similar happen once.
My husband was holding our big female, and I noticed that instead of loosening up like normal, she stayed curled up. Not in a ball per-say, but just a loose coil. I told him to be careful, because that was not normal for her.
Minutes later, she was rubbing her nose along his wrist, then in slow motion she opened her mouth and closed it over his wrist again. Thank goodness he didn't freak out, but he was more than a little shocked, in over 4 years she'd never done anything remotely similar.
She refused to let go, so I had to carefully pry her loose, one tooth at a time. We got her back in her enclosure, and she was none the worse for wear. Hubby's wrist bled for a minute or two, but within an hour you could barely see the mark, by the next day it was invisible.
Unfortunately, hubby never got over the experience, and to this day is afraid of being bitten, even by a hatchling.
Me, I was scared until I got bit, and mine was a pretty hard strike-and-release, I had to laugh at myself for being scared of nothing, and now I don't even flinch when I get tagged.
Gale