Apologies for the delay in replying. You're working with an old version of OCS, and my memory is a little foggy -- I can't recall if I've run into something like this before. Have you tried applying the patch listed in bug 4913?
WRT whether the reviews have actually disappeared from the system: again, I don't remember how/whether the OCS 2.1.x DB layout differs from the 2.3.x line, but my suspicion is that nothing has actually been deleted. Additionally, I don't see anything in the [url=http://pkp.sfu.ca/bugzilla/buglist.cgi?query_format=advanced&list_id=1324&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_status=RESOLVED&bug_status=VERIFIED&bug_status=CLOSED&longdesc=revisions%20required%20&product=OCS&longdesc_type=allwordssubstrbug database[/url] regarding OCS and "revisions required" that might point to a problem, not to say that something hasn't been overlooked. I would strongly suggest upgrading your system to the most recent version of OCS. Additionally, if you could provide us with your submission method (eg. abstract followed by presentation, etc.) and even a link to your conference, I'd be happy to run a test submission through.