Just got some film back from the lab. Upon inspecting it closer at home, there is what appears to be dried mud plastered over one of the frames. I'm not sure, but it looked like somebody stepped on it with a muddy shoe. I tried pouring some water over it and wiping it with a cloth, but the water formed a thick, sticky residue. Now I'm unable to load the negatives into a sleeve because it is so sticky. I won't have access to a scanner until tomorrow so I can't yet see the damage. Why did the water form a sticky layer? Is using water to clean negatives a major no-no?