blasting a refseq protein does not show the protein in the result set
NP_420767 is represented by the non-redundant refSeq protein WP_010919826, which has the same amino acid sequence. This is not very clearly annotated, but if you scroll down to the sequence in the GenPept entry for NP_420767, you'll see the following:

CONTIG      join(WP_010919826.1:1..799)


See here for more info.