Let me get this straight, are you still contesting that the index is actually not part of the dumpfile and I somehow just keep on ‘missing it’?
That is one possibility, yes, but there are others. We just don't have enough data. It would be great to see exactly what pg_dump is doing so we know where the corruption/disconnect is. If you have access, could you try:
psql -c "alter system set log_statement='all' " -c "select pg_reload_conf()"
