You scan for beacons by pulling down on the table view in the RadBeacon app.
If you are not seeing the RadBeacons in the app when you scan, the beacon is probably not in config mode anymore. This is a security feature. For RadBeacon tag, open the enclosure and press the button near the battery. This will reinitiate the config mode for the beacon that will last for 30 minutes. When you scan for the beacon, you should see it.
If you still aren't seeing the beacon then something maybe wrong with Bluetooth on your device and you can try clearing it's cache by turning Bluetooth off and then again.