oid file, but no pg_class row for it

While dealing with filesystem bloat issues, I found a large file
named 43710738, recently updated and sitting in one of my
database directories,

$ ls -lh ../../../data/base/11259315/43710738
-rw-------    1 dba   dba         1016M Nov  3 17:05 ../../../data/base/11259315/43710738

... with no corresponding entry that I can find in pg_class with
that oid (I thought they were all in there).  I tried dumping the
database, knowing the oids are in the comments, but found
nothing there.  pg_filedump'ing the file doesn't seem to be
helpful, either.

Anyone have any tips on how to figure out what this oid maps to?

TIA.

Ed