Some people just have no sense of adventure.
Having seen a 4mm agenoria kit go from a box of bits to a nicely running loco, they go together very well.
If the neighbour doesn't find it and wonders where it came from, it will give time team something to scratch their heads over if they go there and dig it up in years to come.
Is the low level track at right angles to the raised track the line to Par Docks? If so Punch and Judy would have no trouble getting under the main line to St. Austell