Photos/folders suddenly gone. No question Mark. Not qrey. Just gone. Help!

Can anyone please help with this. It was late and I was on my phone. I may have been closing Lightroom down. A message popped up, one I've not seen in my years using Lightroom, to say my external hard drive was almost full and to make space. This isn't true for starters. It's very large and half empty. Prior to this I'd used an plug in usb DVD drive, which had made things a bit glitchy on my laptop. I feel like it's connected. I closed message down and when I look at my Lightroom now all my images and folders are gone. No previous folders. Nothing in 'all photos' section. My hardrive wasn't listed in the dropdown on the left. So I pulled it up, but the folders aren't there. No grey folders. No question marks as mentioned in other posts. The Lightroom folder is still there in my hardrive however. I can't access it. Via lightroom. I may have pulled out my hard Drive in my panic with the message. I think this is all the facts. If anyone can help I'd be so happy!