I have met one person who family struck it rich like you've mentioned, TT.
During the Indian partition in 1947, they were fleeing what is now Pakistan across the newly created border into India when they took shelter in an abandoned house in an isolated village. Whilst the children slept, one of the adults had a little look see around the large, well-constructed house. They came across a wall where someone had hastily attempted to break the plaster to access something..., they had heard stories of families hiding and secreting their wealth..., so they decided to investigate. Sure enough, a small box containing a serious amount of gold was discovered, and they reached India and took the first boat I think it was in those days, and set sail for good old Blighty...
They are well-known in London now...
There is so many abandoned houses, temples, wells, shrines and suchlike in India, that one could keep busy for the next 50 years and not make a dent. This sort of work could be planned properly there as there are solid archives and documents existing to aid any search but, I have to warn you, the bureaucracy there is atrocious. It is no wonder many try and bypass it using bribes.
IUK