It happens from time to time. Did it once in 27 years and literally hundreds of thousands of landings. Single pilot at the time. When two pilot we had a routine of placing a tick alongside the platform name on the flight plan once a clearance was received. Seemed to work OK, though there was still the very, very occasional slip up. If it is such a problem in the minds of some, how about a flashing red light or some such when the deck is not clear. Still a bulb can fail I guess. Hard to build the perfect mouse trap.