You guys realise that moonshell was designed to access the microSD/SD card from slot1 and slot2 (With DLDI patch IIRC ?) flashcarts ?
AFAIK it was never released to work in DSi mode, so no SD native support, you can boot it, but you won't see it shit after it launch, the last versino of moonshell was released a few months after the DSi got out, so yep, you can't.
EDIT: OR, is twilight emulating a SD card from the flashcart ?