If you do a search I think you'll find they are still there unless you trashed the original ones as you though they had copied over.
What you are seeing is the marker file that was posted on your external drive not the real file on your internal drive. What happens here is the OS will create these files as placeholders on your external drive and then physically replace them with the real file. So when your system realized it din't have room on the external drive it threw these marker files in the trash.
Let's say you thought the files were copied and you threw the originals away and even emptied the trash. If you didn't set up your system to securely erase the trash you can still recover them but you will need to be quick here as the longer you use your system the files locations could be over written! So its important not to alter your system files or even run anything until you recover your stuff.
Now the tricky part! What you'll need to do if find a friend who has a Mac so you can either create a bootable USB thumb drive or connect your system to his via Target Mode. What you'll also need is a recovery app like: Data Rescue either to run on your friends Mac or using a USB thumb drive (you can even buy it already setup on a drive). Then hunt down your files.