Lost all photos

I have a WD external hard drive. As I was editing my photos the external hard drive disconnected from my mac and I lost all photos.(cable was not in socket properly) I tried reconnecting the hard drive but still no photos. I went into disk utility and did a repair still nothing. I tried a recovery program after it found the photos I had to pay for it so I didn't proceed with the process. After reading all forums and discussions, I noticed that my photos were in masters. So I drag and dropped the masters file from my external hard drive into the mac hard drive. The only problem is when I disconnect the External hard drive the photos come up with can't find photos message.I selected find location but still did not work. Please can some one help me as I have over 500 GB of photos. I want to be able to save all photos on my mac hard drive and then import the photos on an external hard drive. I have gone in preference but am I missing something. I have tried adding all photos into another hard drive but the message keeps coming up. Does this mean I have lost all my photos? Is there something I need to tick in preferences or when I am moving master file across do I need to bring across something else? I have also realised that this has happened with movies also. Please can some one help.