Duplicated hash values in mining reward
This is a known bug in the early days of bitcoin.

Was fixed by BIP-30 https://github.com/bitcoin/bips/blob/master/bip-0030.mediawiki

There is a discussion here: https://bitcointalk.org/index.php?topic=216938

And yes, 50+50 bitcoins are missed forever.

In fact, there are much more missed bitcoins. For example, 2500 bitcoins were gone to nowhere 
in block 0000000000000449ee5b94ba7a051caffff5c23d6a03335f6e20e3985b5ffa61