Before I answer I have to say... Malcom D (and the goon squad who are, instead of answering her question, using this as a forum), what the hell? The times have changed, to use 'song' in its literal definition is to give vocalists higher merit than instrumentalists to the less knowledgable.
Aside from that, though, I don't think there is any possible way to find a piece without lyrics online quickly... not without the name or composer.
If you can grasp the style of the piece, though, the era, instruments, and deduce some composers, you could probably find it through intense searching---where YouTube would be a great ally. But there are a lot of classical pieces by composers whose names I know not that I am longing to find, too.
If you can sing, perhaps, or even play by ear, you could find a few music teachers (who **** about **** =]) and play your rendition of it to them... they may know of the piece.
I do like that first suggestion, though, I didn't know such a site existed.
[Edit]: Oh you found it. Argh, I'm always answering questions too late.