Loosing images in Lightroom classic

[Nuke_ET42]

This is a weird one, so pay attention. Not sure if anyone else has seen this issue.

I have my catalog and images on an external portable hard drive. This is because I will often shoot away from home and I want the ability use my laptop to either shoot tethered or offload and review my photos before returning home. I typically don't do much editing on the laptop because I prefer my home PC with larger calibrated monitor. I have used this method for years with no issues.

However, recently when I plug the portable hard drive back into my home PC after travelling, any images taken since the last time the catalog was opened at home are not in the catalog and often have been removed from the portable hard-drive. Fortunately I am religious about backing up all images, so I haven't actually lost any photos yet, but I do lose any edits or flagging/rating I may have done.

What is also weird is I set Lightroom to backup every time I exit. This weekend I was travelling and took a large number of photos, many done while tethered to my laptop. I have three backup files from the weekend, one from Saturday and two from Sunday. When the images did not show in the catalog when I opened it, I restored the catalog from each of the back-ups and none of them contained the images either.

I need to find out what is going on and how to fix it so I don't lose this information and cause myself hours of extra work re-importing the images to the catalog and redoing all of the work I had done previously. 

Many of the images from this weekend I had the client review and mark which ones he wanted. All of that is now lost. Any help would be appreciated.

[Nuke_ET42]

OKay, here's something else. Just for fun, I plugged the hard drive with the catalog and images back into my laptop and opened lightroom classic. The images are back in the catalog. I know it is the same catalog because of the date it was last modified. Could this be due to a version mis-match?  

[Nuke_ET42]

One more update. My laptop was running an older version of Lightroom classic. I updated it to the latest version and opened the catalog. Everything was there and I created a backup. I moved the hard drive to my home PC which I had already determined to have the latest version of LR classic. I opened the catalog and the photos were still missing. I restored from the backup and still no photos. I don't get it.

[GoldingD]

Hard drive failing?

[Nuke_ET42]

No. I had a similar issue with another catalog on a different hard drive and I thought the same thing. I replaced the hard drive and the issue remained. Thanks though...