Exactly. I cant figure out why the guy who finally opened it didnt just keep his mouth shut.
"Three weeks later, firefighters on patrol spotted the abandoned box, one of its doors ripped off, seemingly empty save for some old papers and wind-blown leaves. But upon closer inspection, they discovered an inner compartment, which they opened with a torch and jackhammer, yielding the hidden treasure"
Its possible that there was lots more cash in the open compartment and explain why the secret stash was missed. Just speculating ... ;-)