The don't leave me behind feature may be one of the coolest things about the Hidrate Spark bottle. When you have location features enabled, your app will show you a pin on the map of where you were last paired with your bottle whenever it's not connected with the bottle.
So if you leave it at the gym and get home and realize that you are missing your bottle simply go to your profile in the app. Click on bottles and then See Map next to your bottle to see the last location where you were paired with your bottle on the map. This way you can easily go back and get it.