My guess is you would need to restore the Content Store database from a recent backup and get it from there. If you have a Cognos Analytics Administrator (per user) license, you can stand up a Cognos server (for your use only) on a new [virtual] machine without incurring additional license cost. When you configure it, choose the restored database as your Content Store. Once you can see the agent in your new development environment, recreate the one in your production system manually.
Alternatively, if you're very good with SQL and understand the Content Store database very well, you may be able to avoid creating a new Cognos environment. I have been picking away at such a query all day between other tasks. There are many components associated with agents. I'm maybe 20% done developing the query that should tell me everything I need to manually create a copy of an agent. (So, not having the need myself, I need to stop -- so this won't get done.)
Honestly, it doesn't take 10+ hours to create a VM from an image then install and configure Cognos. I'd go the restore-install-manual creation route.