Bosch oven light cover falling off part-broken!?

When I took out our roast(ed) chicken today, I found almost half of the light/bulb cover part sitting on the chicken foil wrap -- obviously it broke by itself! Is it possible under normal circumstance or something is defective? Thank god the foil was there, it could have dropped on some uncovered food too and not being detected if in small parts! Also, is it safe to use the oven with the broken bit still up there -- may it fall off, or may the bulb itself get over-heated? Please help!!!