The phone events guide indicates this takes place on the weekdays, not the weekends.
However, if you look through the existing comments below, another user (gcoll) indicates in version 3.0 of the game, the stages have changed for each character in order to trigger Joyce's appearance.
The nails issue I can't help you with. Only reason they shouldn't be available for sale is if your inventory is already maxed out on them. In my game, I can still buy them at this time. Danesia is the only place you can obtain nails from.
