If you do not have the originals any more, then there is nothing Lightroom can do on this photo.
Discarding your originals is extremely poor practice with any software, and with Lightroom, it essentially means you cannot do anything with that photo.
In fact, keeping backups of all of your photos is the recommended practice ... the originals on one hard drive and backups (exact duplicates) on a different physical drive.
Try going to library view and in the grayed out photo space top right hand corner is a ! mark click it and you will see a window with the description of the pick that should be there. And the option to locate it if it is still on your pc and there will be where it was last put you can use this to chase the file by hand or use the locate tab hope this helps a bit