my 2 external drives with photos show up in LR5 but all photos are missing. Sometimes the drive light is green like it is working but still missing and usually my drives light is red and is not being recognized. When I moved the photos I just dragged them down from drive c to the external drives that I have attached. It all worked fine at first and I really can't figure it out unless I somehow deleted or moved the parent folder?? Any suggestions?
If you unplug drives on a Windows system, and then re-plug them in, there are situations where the drive can be assigned a different drive letter. This causes the problems you are experiencing (there are other possible causes as well).
So, what drive letter does Lightroom think the photos are on? What drive letter does Windows think the photos are on?