The "last location" of your 530 ( and probably other similar devices) that you can access from the Garmin Connect app (iOS) is a completely useless feature. It only records the location of the device when you "sync" which typically is at the end of a ride.
It is COMPLETELY USELESS to find a lost device, for example, if it bounced off your bike accidentally or for some other reason you lost it/misplaced it. The 530, although connected to your iPhone via Bluetooth when riding does not exchange any sort of GPS location with your iPhone. This is absurd, it should occasionally send GPS data to Garmin Connect , then at least you might have some kind of idea about the location of your device when it was last near your iPhone.