A paired Apple Pencil will remain visible in your Bluetooth device-list; being visible in the device-list does not, of itself, indicate that the Pencil is nearby. A motionless/undisturbed Pencil will also shut-off its Bluetooth connection to save power.
Your Pencil, while paired with your iPad, will appear in the device list until it is manually removed from the iPad. The connection status will show as either Not Connected, or Connected.
Only when the Apple Pencil connection status is shown as Connected is the pencil within approximately 10m (30’) of the iPad.
Remember, even the Pencil if still charged, a motionless Pencil will shut-off its Bluetooth connection to save power; if motionless and undisturbed, the connection status will show as Not Connected. As such, a Pencil only be inches away and out-of-sight will not be detected either visually or by your iPad.