http://www.d20srd.org/srd/skills/spellcraft.htm
I'd just like to leave this here. This thread has been going on for very damn long, in a discussion which
should now easily be solved by what spellcraft is. You /need/ to see or hear the components, otherwise you'll
just know the spell is happening, when it already happened.
I wouldn't necessarily quote this as dispositive of anything. If you notice, that particular wiki also discusses using "read magic" and "detect magic" spells, neither of which are part of the NWN system.
It is always tempting to try and cross-pollinate from various sources, looking for the one that supports the position you want to support, and citing to it. However, as a baseline issue as far as how I choose to role play, I don't subscribe to any set of rules that seeks to handcuff players into playing a particular feat or skill in only one particular way.
In that vein, if a player wants to use spellcraft without seeing or hearing, go for it. If a player wants to have a wizard that doesn't cast from a book, go for it. Heck, if someone wants to make a wizard that is blind and deaf, go for it. Make life interesting.
Also in that vein, play a sorcerer however you wish to play a sorcerer -- but know that by doing so, you have a corresponding obligation to try and not circumvent the in-game drawbacks that are designed to impact your player (in other words, play honest -- if sorcerers are distrusted in Dementlieu, then no one should be trying to cheese their way around that. Trying to role play that difficulty is the pinnacle of good RP).