hg log FILE doesn't find all entries

[Boylan, Ross]

Issuing the command "hg log sync.py" did not show me all log entries with that file name.
In particular, it doesn't show the current rev 19, but 
<terminal>
ross at tempserver:~/src/FS$ hg log -v -r 19
changeset:   19:b5a0082641dd
user:        ross
date:        Mon Sep 09 19:30:38 2013 -0700
files:       sync.py
description:
Initial revision
</terminal>

Can anyone explain what is going on? The repository is a bit of a mess, which may have contributed.
r0-3 are a mercurial respository created out of the current version of the project on one machine.
r4-30 were imported from an "unrelated" repository created by converting rcs->cvs->hg with the history of the project + some contemporary changes on another machine.

The rcs archive does not appear to have any branches on it.

Theories:
1. sync.py refers to different objects in hg's opinion.  However, hg log reports sync.py in both the 0-3 and 4-30 sequences.
2. The conversion process has messed things up.

I've been trying to get a cleaned up history using rebase; this particular problem occurs before I do any rebasing.