The 50 coin block doesn't exist because those 50 come from the genesis block, which can't be spent:
"This was probably intended as proof that the block was created on or after January 3rd, 2009, as well as a comment on the instability caused by fractional-reserve banking.
The first 50BTC block reward went to address 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa, though this reward can't be spent due to a quirk in the way that the genesis block is expressed in the code (this may have been intentional)."