The only way to get rid of the orphaned "ghost" photos is to delete Photosmith and reinstall from the App Store. These are photos which are still referenced in the Photosmith catalog, but the thumbnails are missing. This happens from time to time due to photos which we don't correctly remove during a delete, or from a reinstall from an old iTunes backup.
The best option is to first make sure all your modified metadata in Photosmith is backed up by syncing with Lightroom. Then delete Photosmith and reinstall from the App Store. You will then be presented with a clean Photosmith catalog - you can then sync your Lightroom User Collections to get your photos back onto iPad.