Not necessarily, but many fish and other inverts like crabs look at shrimp as something good to eat. Also, to grow shrimp need to molt. When they molt they are very vulnerable until the new shell hardens.
Are you sure they are gone? If so, have you pulled out dead bodies or just don’t see them? As DK said, many predators, molting, hiding, jumping all could be the cause/reason. When they moly they hide for a few days till their shell toughens up
