Elegan - Repair - Disc

All i can say is that the design of disc brake is totally crap. Your pad can just fell off its housing once the pad is just half worn out. This is due to non existance of nuts or bolt to keep its pad on place.  The pad just slotted and holds with a spring.

Once your pad gone, the disc motor pump will press onto the brake disc resulting premature wear and tear.

So, get your brake pad checked and replaced immediately when it emits cracking sound.