That's good to know, some useful context:
tldr: It's going to take a while
The search area is immense. People (even locals) fail to understand the incredibly vast distances. Sure, you can think up a comparison from your own context of a few hundred kms... but does your example have nothing, and I mean, literally nothing manmade but the road infrastructure itself in the proximity of the horizon for sometimes hundreds of kms? Few places do. In more remote places than this, say in the Kimberly, you might as well be on the moon. There's nothing out there to support you or resupply you; you always have to think about that ahead of time.
It's the middle of summer here, we are approaching our hottest month (February). Pavement, being a heat island, makes working alongside or on it a slow process. Exposure and heat stroke are real risks.
On the upside, the roads are sealed, and in relatively good condition and well designed when compared to say much of the US or the poorer parts of Europe but the odds that it falls into a crack or pothole will scale with the distance. A vehicle-mounted detector makes obvious sense but could be costly. However, as we know, especially at these temperatures, roads are slow moving rivers. It might even become embedded if it did indeed land on the surface. In which case it sounds like we may never find it.
Assuming it's most likely in the literal middle of nowhere. The risk of a member of the public coming into to direct physical contact would be highly unlikely. There are sections of road that haven't had human feet walk on them since they were last poured. But that introduces an interesting problem. What happens next time maintenance replace that section? Do crews need to be wary of digging it up, possibly aresolising it in the process? Maintenance is probably the most likely human contact scenario. Does every safety management plan now include the incredibly remote chance of finding it?