Please make sure you have the correct catalog open(File>>Open recent)
Click on Previous import from panel on the left in Library module.
If so check what is there Previous location by clicking the "?" on top right of the image thumbnail.
Search the files by there name on your computer from Explorer/Finder(with your external drive connected).
Please refer Missing Files « Julieanne Kost's Blog
In addition, if I take the external hard drive and plug into my lap top ( Macbook Pro) , Lightroom finds the photos , and does not show the question mark. However, I still can not see the photos on the external drive.
You could then re-export them to your External drive(with out renaming).Then reconnect them in Lightroom
Thank you for the reply Akash.
I have done as you instructed .
When disconnect the drive and click on " ? ," it shows the external drive as the previous location.
When connect the drive and search using the finder nothing is found.
When I connect the drive, Lightroom see the files and works as normal .
Lightroom sees the files if the external drive is connected which leads me to believe they are still on the drive. However, they are only able to be accessed by Lightroom . I can not see anything in the folders on the external drive.
This really has me baffled.
I will just export back and see what happens. Thanks for that suggestion, as it never occurred to me.
Exported back, all seems okay now. Thanks for the prompt reply and the help.
Glad to help