since i started the game and loaded my lvl 35 char (now lvl 48) there is no sceleton key recipe anymore avaible at the blacksmith craftwindow, cant get any keys anymore and don't do dungeons so...
is there a second way to get it?

1. Check different smiths. For example, legion smith in fort ikon can do dynamite, while the one in Devil crossing can't.
2. Doing this quest on next difficulty would give recipe again.
3. Doing this quest with another character would also give recipe, all formulas are shared.