I would start looking at the records for some bank robber who got shot and nobody ever found the money.
Stashing your economies inside a house, in a safe, I can understand... but in cans, under a tree? This is the kind of thing someone on a getaway would do. The coins are fresh out of the mint too, so it's likely the entire stash came from one place.
In the article it says they're stashed in chronological order and almost all immediately that they were put into circulation, ruling out a "big heist".
Yes, the fact that nobody ever successfully came back for this is fascinating. They either buried it such that the marker was soon lost and or buried it in a big hurry, never meant for it to be found (in their time) for whatever reason, or died before they could recover it.
Stashing your economies inside a house, in a safe, I can understand... but in cans, under a tree? This is the kind of thing someone on a getaway would do. The coins are fresh out of the mint too, so it's likely the entire stash came from one place.