PostgreSQL: Restoring 1 file from a directory format dump
I found the line in the toc.dat file that made the call and unpacked
  the .dat.gz file to find it only contains "\." (sans the quotes) in
  it.


\. is not a command, it marks the end of data in a COPY stream.
If the corresponding data file inside the dump contains only that, then the source table was empty.

Also note that you can pg_restore --list to list the contents of a dump in directory or compressed format.

You may also restore the contents of an individual table into an SQL file rather than in the target database, then modify that file as convenient, and play it into the target. See the pg_restore manpage for more.