The 'Craft Lost Cure' mission gives you The Lost Cure temp power, which is then required to beat the following mission. If you somehow manage to lose The Lost Cure power after beating 'Craft Lost Cure', then you'll have no way of replaying that mission to get the power back and the arc will become unbeatable. The finale mission also lacks the usual option to autocomplete.
 
	 
 
	As for how I actually managed to muck this up... I was having trouble finding lost spawns so after several minutes I went to the mission architect, made a map with lost enemies, tested it, and used the cure on them. The mission pinged complete but upon leaving the architect I was still sitting at 0 out of 20 lost cured, and the temp power to cure them was gone.
 
	 
 
	There's a moral in there about being impatient I'm sure, but the result is that this character can't access the midnight club content and their clues menu is filled with (pretty lengthy) clues from the Castanella arc that never went away, making that menu a pain to navigate.