It's possible that:
* The name is slightly different: Perhaps it's a different year, or a different venue, or a variation on the title like "Tonight at the Opera with Opus".
* It's a local production: It could be a smaller production put on by a community theater or opera company that isn't widely known.
To find out more, please provide me with:
* The full, accurate name of the production.
* The location and date of the performance.
* Any other details you can remember, such as the opera company or performers.
With more information, I can help you find the cast list.