It's just a case. They're meant to protect from minor every day impacts. If you want something that can protect your phone from something as extreme as falling off a bag while riding a bike you're gonna need a really big really thick case with a bunch of shock absorption. If OP was riding a bike that phone was moving pretty fast when it fell and was fairly high up. All that energy has to go somewhere and some plastic with a bit of air is only capable of doing so much.

When I used to ride bikes I had my old Galaxy nearly snap in half when I crashed one time.