i had ~600 pictures edited in Lightroom, then i tried to import a couple more into that collection. When i did that, all the picture edits and pictures were missing. The pictures are still on my computer, but the edits are gone. I didn't save the collection. are they gone??
If you are referring to the system collection "previous import", this always contains the last import you did. The new data replacing the old.
Your images are really in the folders and collections you placed them in previously.
If this is not what you mean by "missing", please describe your situation in great detail. Attaching screen shots can be helpful.