Unfortunately, Unicode doesn't seem to have a ct ligature. This is for a sensible reason; Unicode is meant to be about characters, not glyphs, and in theory shouldn't be encoding such things. But ﬆ made it in anyway, as "character" 64262, and it's too late for them to remove it now. (They probably wish they could.) I'd like to ﬆart using it in my LiveJournal poﬆs, but without being able to provide ct ligatures as well, it juﬆ looks silly and inconsiﬆent.
Addendum: I prepared this poﬆ in TextEdit, and when I used the Find command to search for "st," I found that it correctly counts "ﬆ" as a match. That's both pleasant and surprising.