i stopped spinning as i was going over small bumps at about 18mph, one bump made my body hop off seat, my shoes came off the pedals, and so did my chain in the front. is this normal? or some problem that needs to be addressed on my bike?

could this have been prevented by spinning over the bumps in a bigger gear?
i was wearing regular sneakers this ride and if i was clipped it i probably would have kept spinning to create force in the chain