On October 24th 1978 I flew a Chieftain (VH-MBT) as part of the search for that aircraft. Unusually, we found nothing despite combing the area for hours. I've been in a few searches over my career and we always found something, however small.
When Dr Ian Tippett disappeared in a PN68 off Wilsons Prom we found an oil slick and a few seat covers. With young Fred Valentich, not a trace. Certainly a strange one.