Today I was loading my 5x4 film holder with some Ilford FP-4+ sheets, and as I was removing a sheet from the box, it appeared to be stuck to the sheet under it, with a bit of coercion it came loose, with a tearing "sticky" sound. At first I thought it was some sort of protective paper placed inbetween the sheets, but when I'd loaded the holders (with the next sheet from the box) and opened my changing bag I found a strange looking sheet of film.

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I scanned in the sheet (the image) and as you can see it appears as if parts of it has simply torn off, and there's a wet-looking darker blotch covering quite a bit of it. Does anyone know what might have happened here?