I doubt it was waterproof. To my knowledge, those are only used for toddlers and seniors to protect mattress from accidents of the bladder / bowels variety.
Not the OOPs I just killed my wife variety.
(My aunt bought "Out!" Pet Stain and Odor Remover in the economy refill size at Wal-Mart when my uncle started having "accidents" -- she said it was very effective for cleaning up after him.)
Out is good, but we find Nature's Miracle even better!