(Sorry for the english answer, I can read spanish but I'm will working on my grammar)
Nope, if you cancel a story quest you cannot get it back, though usually the items are still around (at least the mayors pants are, because of the new changes to how you get them)
For other quests like the bulletin board the quests are created randomly and could appear, the special orders board and walnut room quests are always of the same set of quests and cycle around so you'll eventually get them again (if you've never completed them, and most appear even if you have completed it before)