It took me a little over four years, but I finally located a numbers station on one of my radios. I wasn't intentionally searching for such a broadcast at the time; I was just randomly scanning the shortwave band on my diminutive Kaito KA11 radio. The frequency was 5900 kHz, SSB wasn't required, and this took place between 0830-0843 UTC on 04 August 2009.
I believe that I heard the V02 numbers station, which supposedly originates in Cuba. V02 uses a female voice to recite digits in groups of five, with about a two-second pause between the number groups. I listened to some of the YouTube videos described as V02 recordings, and the voice sounds the same as what I heard.
Unfortunately, I tuned in after the beginning of the broadcast, which might have contained the well-known "Atencion" greeting. But I heard the end of the broadcast, which gives me more confidence that I heard V02. In my logbook, I wrote that the broadcast concluded with what sounded like "two nine, two nine" or "goodnight, goodnight". But a YouTube video that's believed to also contain a V02 broadcast contains the same ending as I heard, and is transcribed as "final, final".
The Spooks Newsletter website has a pseudo-schedule for V02, which lists 5898 kHz as a broadcast frequency beginning at 0800 UTC on Tuesdays.
My KA11 was switched off, and I tuned in with my more powerful Eton E5. I captured a video recording of the final minutes of the broadcast. The E5 backlight only stays on for 15 seconds at a time when running on battery power, so the screen is not illuminated continuously in the video.