Isn't it time you are taking classes for Lightroom?
Do you also have a real question?
I have been using LR since it came out, Version 1, and never lost any images.
You aren't doing something right. LR doesn't indiscriminately delete and or lose images. It is a Database system that catalogs your images. If you have thumbnails that are grayed out and or with a ? Mark that means the program has lost track of that image. That only happens if you moved it using some other program. Deleted it using some other program. Disconnected the external drive the image/s were on.
That same question is posted by people that do not fully understand how LR works and how to use LR properly. If this was a car you would need a Drivers License to operate it which you would first need to pass a test showing you know how to properly operate, drive, a car.
You are in the Import dialog window, Why are you there? Are you importing new images? Have you MOVED images around on your hard drive using a File Manager?
Yes LR thinks the images you are trying to import or duplicates, Copies, of images you already have in the catalog. Are they? Just because an image is grayed out in the Library module doesn't mean you have to import them again. The graying out mean LR can't find that image in the folder it thinks it is in, IE where it was originally when imported. What did you do to make that happen?
I have images going back to 2004 on my computer. LR has never lost any of them. Have I had images display grayed out and with a ? mark? Yes I have. That was because I moved them from one drive or folder to another using a File Manager outside of LR. Once I pointed LR to the new location of those images the ? mark, and gray state, went away.
Exactly what I meant ... in rather short words
I'm using LR since version 1 too ... and never lost any image.
Agreeing with the others ... Lightroom doesn't lose photos, it has never happened to me.
I use the following very simple method to make sure Lightroom doesn't lose images ... I put the photos in their destination folder right out of the camera, and I never move or rename them ever! How simple is that? Less work than moving photos around, and you never lose them!
Same as the others here; I have used LR since it first came out. It did lose a folder of images once, but that was my fault, I moved the folder outside of LR. A simple search in LR and these images were reconnected. You do need training; I belong to KelbyOne - A better way to learning Photoshop, Lightroom and Photography. They have several great video tutorials on LR. You can join for a year, or for only a month, if you want, or even rent particular courses.