Not sure what you are trying to say here because the hatchery, if it was one, or the hatcheries, if it was both on Spring Creek inherited the mud snails from Spring Creek and it was not the other way around. Given that the source in Spring Ck wasn’t the hatcheries, what source(s) would you then suspect?
As for cleaning gear in the recommended ways for appropriate biosecurity, since some never do so, then perhaps they would at least check beneath the wading boot laces and check inside the boot because the snails are frequently found mixed with sand and other debris that gets between the stocking foot and the boot. I know this from PFBC biologists telling me that those are two problem areas that they have experienced during surveys for mud snails. I assume that anglers rinse such materials out if they happen to get in the boot anyway. Anglers should also and can easily rinse off the mud that lodges in the lugs of the boots since the exposed snails in the lugs can get buried/covered in that mud as they leave the stream.
And by the way, one of my biologist friends and former colleagues has yet to find a mud snail in or on his boot foot waders during mud snail surveys. I was at ****’s last evening and saw boot foot waders for $100 and hip boots for $50.