Does it seem a bit strange that both black boxes weren't found fairly quickly once the SAR forces were on the spot?
Black boxes do not transmit their position unless they are under water (due to triggered Under Water Locator Beacons).
Only deployable Flightrecorders (which are mainly used in military aircraft/helicopter installtions) have ETL's installed which transmit their position (or the position of deployment) on 406 MHz to the satellite for locating the black boxes).