I can come up with a long list of these from my Southeast Asian promo notes, so I’ll mention cases which I can directly pull from my head.
- Traditional Chinese Dedenne GX promo with Hong Kong Regionals stamp
- Traditional Chinese Regigigas promo with Hong Kong Regionals stamp
- Traditional Chinese SM-P promos from 063/SM-P to 082/SM-P except 064, 066, 073 and 074
These slots are presumably allocated for the Gym promo set which accompanies the release of the last major SM set in Asia AS6a/AS6b. However as all Gym events were cancelled at the time due to COVID, only the 4 GXs in the promo set were released in Traditional Chinese in a separate event after Gym events were reinstated.
We are able to speculate most of the remaining cards from the Thai set, however whether these cards were actually printed remained a mystery.
- Thai SM-P promos 098/SM-P, 099/SM-P and 106/SM-P
These share the same story as the Traditional Chinese SM-P promos above: the same promo set was allocated to slots 094/SM-P to 113/SM-P, and 15 out of 20 cards in the Thai set were released in a separate event.
However, out of the 5 unannounced cards 2 were later found sold by a local card shop in Thailand (110/SM-P Blue’s Tactics and 113/SM-P Roller Skater). I tried to ask the shop if the remaining 3 also exists but never got a reply.
- Thai 7-11 Pikachu promo, Charizard VMAX Rainbow Rare and Espeon VMAX Alt Art
3 Thai Full Art promos very well known on the forums as they were listed in official card lists but never actually released.
- Indonesian Indomaret Sword & Shield promo set for S5 release
The official Indonesian card list also had the same issue of including cards whose release was questioned (although no such cards in the Indonesian list were chase cards). The Bulbapedia diff page below shows the change made by me during an official card list update in 2022 which added several cards whose release status was unknown.
The Indomaret promo set which should be released alongside major sets S5I and S5R was among the questioned cards, with none of the cards revealed until the official list revealed them a year after, and not even one card from the promo set could be found in marketplaces.