Pretty sure I've checked everything multiple times.
SHOP 0x0 label26 [2,8] 0x18
SHLI 0xblah 0xblah 0xblah....
Even checked these in the Hex Editor and they are properly written
but no secret shop triggers at the location (while also carrying the card of course)
And to make sure I didn't mess anything vital with the card
I went and entered all the secret shops on the world map. No problem.
Even tried different tiles at the intended location
(each time reloading from a savestate before the game loads the next floor)