Interesting that it took more than 3 weeks before I found this thread. Especially because english is not my mother language, here is a copy/past of my comment, which I left under DJGigabytes video.
Hi, I am GrollenKette951, the person who found this lost card. (If you imagine that this mystery started nine years ago when I was seven.)
It’s nice to see that my efforts to find this card are so appreciated. Here I posted all of the undistributed cards: https://twitter.com/GrollenKette951/status/1269168384673013760
For everyone who is interested in how exactly I found the card or who didn’t find the explanation in the video enough, here is a more detailed version with approximate duration of each step.
So where do we start best?
I started the search on June 3rd (Search time: Around 30 minutes):
The first thing I knew was that Zoroark (www.pokemon-card.com/assets/images/card_images/large/BWP/027277_P_ZOROAKU.jpg) was the last BW-P promo before the lost cards. Note: The Japanese card database uses the abbreviations P for Pokémon, T for trainers and E for energy cards. The name used for all Emolga cards is EMONGA. From there I simply tried out all the numbers and then came across the unreleased Emolga card.
The next number had to be Druddigon. And that was it.
June 4th (Search time: Around 2-3 Hours): Knowing what numbers the energies had, I was able to narrow down the search to BWP/027328, so I started trying out every Gen 5 Pokémon and a few classics like Pikachu, Mewtwo etc. At that point I was already afraid that the card could be a completely unknown trainer card and went to sleep. (Solving this problem with a program is possible but takes much too long (30 Letters á 26 Options)
June 5 (Search time: Around 30 Minutes): After sleeping and finding some other scans for PokéWiki, the search continued. I started trying out all the trainer cards in their release order since the first Japanese black and white set. At 7:36 am CEST I found the card and posted it with a “YES, YES, YES, YES, YES, YES, YES :party:” on the PokéWiki Discordserver in a semi-public channel. Reddit (r/pkmntcg), Bulbapedia (and the Encyclopaediae Pokémonis community) and PokeGuardian received the information next.
A little update to this comment: Thanks to somebody else from PokéWiki I now have a programm that automates the whole Emolga step (as long as I know the card name, the set and and an approximate search area for the internal numbers). And togehther we came to the conclusion that automating the second step would be very inefficient.
If somebody has some good ideas to what an potential prize card could have been, I might search under that name in the card data base.