It's possible that:
* The title is slightly incorrect. There might be a similar title or a different year for the film. You can try searching for variations like "El Corrido de Valente," "Valente Quintero," or "Corrido de Valente."
* It's a lesser-known production. It could be a short film, a local production, or a film that wasn't widely distributed.
* The film never got made. Sometimes, productions are announced but never come to fruition.
To find more information, you could try searching online movie databases like IMDb or the Internet Archive using different variations of the title.