A few things don’t make sense in relation to the phone.I don't think it has ever been confirmed that there was a phone ping at 5pm?
Even if it is correct, there's no way of knowing if that 5pm ping was before or after the phone had been chucked.
Do we know whether the phone was in the (dam) water? Has that been confirmed? The condition didn’t suggest that it was in muddy water for 3-4 months. It was photographed on the edge in mud, in autumn/winter, when the water level would be possibly higher than summer (unless water source but not pumped in winter). Considering 40c days in Feb. The targeted search earthworks appeared to clear blackberry bushes between road and dam. Is it possible that it was thrown in bushes with other belongings and moved when blackberry bushes lost their summer density? and the risk of being found increased? Or was it planted? If it wasn’t in water, would it have been traceable using the imei once battery died? It didn’t appear to be damaged as you’d expect in those circumstances, especially by an Electrician.