It's possible that it's floating just under the surface, in which case the radar reflectors won't help. Radar also isn't necessarily _great_ at finding anything bobbing in waves, as water will itself reflect radar.

Additionally, if the problem was a power outage then the radio also might not work unless it had a separate power supply.

Emergency beacons cost a few hundred dollars and are designed for this purpose, not having one is pure negligence.

If they're on the bottom of the ocean then even if they're found a rescue is unlikely to happen in time.