No, just because a spell is shown in Lucy does -not- mean it is live. I could point you to a huge heaping pile of spells that Lucy knows about but which are not live in any way.
A -reasonable- but not perfect method to determine if something is in game is to look to see if there are any "items with this spell" - if it shows a spell scroll, there's at least a -chance- the spell is live. If the spell scroll shows a -source-, then it's pretty much definitely live.
But there's no perfect way to tell, really.