Update your version of LR. Is it now at 2015.7. Use the Creative Cloud app to do the update.
Oh Never mind. The newer versions of LR aren't supported on OS X 10.9 and below. You'll need to upgrade OS X to either Yosemite 10.10 El Capitan 10.11 or the newest Sierra 10.12.
Not sure if those older versions are still available or if your model Mac can run them.
As to your specific problem I would start by checking your hard drive. Once LR imports images they never leave unless you specifically remove them.
Show a screen capture of the above photo in the Library module with the Folders panel open/visible.
Sounds like after import you are either changing the folder name of the file location Lightroom knows about or you are disconnecting/removing the drive that the files are on. Then Lightroom will consider them offline and you will not be able to edit them.
You need to either reconnect the missing drive or tell Lightroom the new folder name.
Thanks for your reply. Just so the info is correct I am not using any external drive all these files are being saved onto the Mac I am using. And I have not moved any files around in the catalog.
I am running OSX 10.9.5
On your filmstrip it shows the ! mark in the top right corner of each thumbnail which is an indication that the files are missing.
Click on the ! badge/icon for any of those thumbnails.
It will bring up a popup that will tell you the previous location
Look for that previous location in Finder or search finder for the original filename... then you can update Lightroom using the locate button
Follow the more detailed procedure below to Update Lightroom with the new location of missing files:
Unfortunately, the files are missing from the catalog and the original import location shows no trace of the files even though it should. I never moved any files around and the problem just occurred today. Net loss of 150 images. Thanks for that though, it was the closest I have come to solving this problem
recurred again today* sorry for the typo
*Reoccurred wow I feel stupid :/. It happened again is my point
Could your import be set to 'Add' instead of 'Copy'?
Ok where did you import them from, memory card, camera connected directly to the computer or from a hard drive after copying them from card or camera?
What was the option you chose at the top of the import dialog window, Copy, Copy as DNG, Move or Add?
What folder did you store them in if Copy, Copy as DNG or Move was selected in the import dialog.
If seems the images you seem to be missing are in the LR catalog so they were imported. But if you had Add selected from a memory card or an external hard drive and then you disconnected that drive or took the memory card out they would go missing.
Please show a screen shot of the Library module with the folder selected you think they are in.