Hello, can you be a little more specific with what you are trying to attempt? I think I know what it is that's frustrating to you...I have noticed that when I open Lightroom and import and edit photos, and my program closes unexpectedly for some various reason, when I try and open my program to continue editing them, I find that I can't do so because it won't let me open them, it states that the images are already imported or are in another catalog or something to that effect.
What I do in that situation is I create another/new folder and move the said images into that new folder and re-import them from there. I would suggest moving them rather than copying them, if you copy them the program may not read them correctly as being new images. Sadly, I usually have to start over with the editing, but those things happen from time to time. Another note I wish to point out is that there's a check box in the right hand side when you go to import images, either new or ones you've already worked on, that says to ignore duplicated images. If you have that box checked, you should be able to see all of the images at once.
I'm assuming that you haven't deleted your original files from your camera/memory card until you have finished editing them in Lightroom? Always, keep them on your card until you have edited them fully! Trust me, I speak from experience...anyways, I hope this is of some help. Have a great day!