I'd feel like an ****...and **** who also had a 350 Monaro in the shed.
It used to happen a lot with cars and bikes, but now even old grannies and grandpas get online and check stuff out, so it's rare to stumble across some old person with a "hidden classic" for a low price.
The last time I saw it happen was with a pinkish colored six cylinder XB coupe...steel wheels, really good nic, which a wrecking yard had bought off an old lady for $3000 and was selling for $9000. This was back in about 1990.
It still is a standard thing for swap meets...everyone wants to stumble across some treasure that the owner has no idea of the value.
A couple of years back I tried to get myself a bargain, as I knew a farm on a remote road where you could see a VH Valiant Pacer sedan sitting in a shed. It'd been there for at least ten years, and I thought "to hell with it...I'll ask", and rode my bike to the farmhouse. I started out by introducing myself and asking if the guy had any old motorbikes on the property that he might want to sell, and he took me to the shed beside the one where the Pacer sat. He had some old Ag bikes and also an old Triumph which needed a full resto, and as we chatted, I broached the subject of the Pacer. I had a bit of a look as we stood there talking bikes...it looked great, very straight, and only had faded white paint with the original striping in good condition, and said "How much for the old Valiant?". He said, without a blink of hesitation, "The 265 Pacer isn't for sale, but if it was, it'd be $30,000..."
Oh well...