Here's something that might help:
If you take a look at any file under control by the dssc (ls -l) that you haven't yet checked out, you can easily discover that the file is actually a link to the vault.
So, when you actually populate a file by using dssc pop -get -uni, what happens is that the tool goes to the vault and fetches a local copy for you.
Now, the above sentence has the actual answer to your question: all you need to do is to actually use dssc pop -get -uni one more time... Well, the tool will probably disagree, recognizing that you've tampered with the file and prompting you to use the -force switch if you really want to revert (repopulate) your file.
Hope this does the trick.