Hi,

You cannot remove DRM from existing videos that have been previously downloaded. Unfortunately since there is no way to obtain encryption keys for it, you need to download it again. But since the title has been retired, that is no longer possible (>_<); Something to mention, the Multi-Search feature coming to the Patreon edition of Jav-It (soon) will allow you to search for your missing title across multiple web pages. It is likely that one of those pages will have magnet links that can help you replace the DRM copy you paid for.