Is it possible when we use someone's compiled version of bitcrack and they modified the source code like that "if addr is = 16jY7qLJnxb7CHZyqBP8qca9d51gAjyXQN email me xyz@hotmail.com and print reached end of keyspace" something like that 
So We do not know that we have solved the key. And does the compiler get the key without knowing us
So We do not know that we have solved the key. And does the compiler get the key without knowing us yes , compiled exe can do it .... only use net socket connect to his server....
like Trojan Virus .....
but 0x8000000000000000 is very big number ....
we have no super GPUs to find #64 private key .... possibility is very little
16CeETE9dHgj73GBEk53Lf2Cbz5EAjyXQN C006D1E4ADD746D8
16CrWvhAvU7RPsRj4WLo1tmzTsZtAjyXQN FA3229E25C676458
Last few characters have little similarities if we are able to guess few characters of key from back or front we will be able to solve atleast p64.