Brake pads are consumables and wear out, it's nothing to worry about.
Like Mr Beanz I've work out pads in a single ride due to large descents, wet weather and the ride leader using the infamous words "I know a shortcut" which turned out to mean a mile of sand and grit. This doesn't stop me riding in the rain and grit, I just carry a spare pair of brake pads and keep and eye on the rim wall thickness.