I imported about 150 photos today from a shoot into Lightroom, and began to edit them. A few hours later, I got a message on my computer that my hard drive was full, so I made space by deleting some old files. When I opened up Lightroom, I found that all of the photos from my most recent import were "offline or missing". I attempted to locate the photos, but when I searched for the file names in finder, nothing came up. Unfortunately, I had formatted my memory card since, so I cannot retrieve them from there. Any suggestion
You need to search using your operating system's search feature. If that doesn't find the photos, they're probably gone. You then need to find an "undelete utility program", install it and then run it to see if it can recover your photos. Run it on your hard disk(s) and on the camera card.
In the future, you should not be deleting photos from the camera card until you have 2 copies of each photo, an "original" and a backup on a different physical disk. Also, once you import photos into Lightroom, you need to do all photo management from within Lightroom and not in the operating system.