It definitely drops, at least pre 5.5. After the initial fix it took me 34 runs to get it. Looking at https://arrtripletriad.com/en/card-edens-promise it seems like the drop rate is still VERY low since people commenting there have done many more runs than I have and still haven't seen it. Unless something in 5.5 has broken the drop again, I'd say it's just a case of RNG just being really awful.