FYI:  The first 54970.38 billion pages on directory.io have already been searched for active Bitcoins and a few were found.  Most if not all of the bitcoins found in these first 54970.38 billion pages were placed there on purpose as a sort of "canary in a coal mine" test of the security of the network.

See the search project (started at private key 0 and searching the private key space linearly, currently running about 21.10 trillion keys per day): 

https://lbc.cryptoguru.org/stats

And the "puzzle transaction" security test is discussed here: 

https://bitcointalk.org/index.php?topic=1306983.0