Losing to the elements:

I will assume your gun was acceptably accurate and reliable with the Buffalo ball since you chose to go afield with it.

Therefore, the problem of it not going off was strictly the wet environment. With any muzzleloader, keeping it covered in foul weather range between absolutely necessary (flintlock) to highly advisable (the most modern closed breech m/l).

Having hunted in up to a downpour (1" an hour plus), you can keep your gun working, but one or more layers of protection need to be used.

1) Keep the muzzle down, no need to invite water down the bore.
2) A Cows knee or similar lock cover; slows your shot down.
3) Shelter you gun under your rain gear, pancho, etc.
4) Check your lock area every 30 minutes or so.

Hunting with PRB:

a) Things have to fit tightly. I tightly patched round ball can be every bit as difficult to load as a sabot in a clean bore.

b) Patch material is the key. I has to be tough, and the right thickness to meet item a). Pillow ticking, self cut, or pre-cut is as good as I have found.

c) Lube as little as necessary. I have used everything from Crisco, to wax based ball lube, to bore butter, moose milk and spit. They all work, but too much will diminish your charge, and make a mess of you and your gun.

d) Know your limits. The PRB kills as well as anything, within it's limited range. It sheds velocity quickly, so, depending an the initial velocity and the ball size, sight in at a conservative 50 to 75 yards and plan get close and wait for good presentation.

e) Be patient. Time spent waiting for a reasonable shot is time well spent.