I've caught such large worms. We called them fiddle worms due to the manner in which they are caught. We'd go into damp areas with lots of leaves on the ground and many small saplings growing. This would often be along a river or creek bank but always at least close to water.
You take a handsaw with you and the coarser the teeth the better. You then saw off a sapling perhaps a couple inches or so in diameter about 24" to 30" above the ground. Then you begin slowly sawing down thru the stump making it vibrate as much as possible so the roots send out vibrations into the ground.
If present the worms just boil out of the ground. Average length is closer to a foot but it was not at all uncommon to get them 18" or more in length. I've not done this in many years so don't know how common they are anymore.
