Separate normal privacy from a warning
Shrimp hide after being introduced, during or after molting, and when the aquarium has little cover. Dense plants and hardscape can make a healthy colony less visible.
A sudden change affecting many shrimp may point to stress, a predator, a sharp light change, or water-quality trouble. Check whether feeding and grazing continue.
Investigate gently
Test ammonia and nitrite, verify temperature, and review recent maintenance or additions. Look for fish investigating the hiding places or a filter flow that has changed.
Avoid lifting every rock to count shrimp. Disturbing the tank can add stress and make it harder to see how the colony behaves in a settled environment.
For your own tank
Add cover where the shrimp can retreat without blocking circulation or making the whole aquarium impossible to inspect. Try observing at a quieter time of day. If hiding begins suddenly across the colony, compare behavior with a recent timeline of changes.
Use these as general hobby references. Test your aquarium and confirm product guidance before making changes.