Okay, I've hacked together a solution that resolves my problem:
I grep'd for messages with a range of Date: fields
This gave me all message from the 20th through the 23rd, which is what I wanted.
grep "^Date: [a-zA-Z]*, 2 Oct 2009" */* -l > list.txt
Then, I use the following script to pump each of those files found into a folder named "Recovery" in the user's mailbox:
I ran this script for each user that wanted all messages re-added to their mailbox. I'm sure the script could have been modified to include the grep, get the user's zimbra ID and account name, clean up, and repeat this for each leaf within store/0/<zimbra id> ,but I had to slap something together so I could get the job done quickly.
for i in `cat list.txt`
/opt/zimbra/bin/zmmailbox -z -m email@example.com addMessage /Recovery /opt/zimbra/store/0/<user's zimbra id>/msg/$i
I hope my experience helps someone else.