Your photos were never "in" Lightroom.
When you do an import, the photos are referenced by the Lightroom catalog (which is a database), and no new copies of the files are created. (unless you used the "Make a second copy to" option when importing).
So when you deleted the originals, they are gone, except if they are still in the Recycle bin/Trash, in which case you can restore them.
All the work you do in Lightroom is done with previews, and the previews from the Library Module can be extracted.
Unless you chose to create 1:1 previews, they will have smaller pixel dimensions than the originals.
See Jeffrey Friedl's Blog » Jeffrey’s “Extract Cached Image Previews” Lightroom Plugin