I created a catalog and uploaded some photos from a folder and edited them. I forgot to upload one photo from the folder so I imported it into lightroom. All the previous photos I was editing (the ones in the bar on the bottom) disappeared leaving only the one photo I just uploaded. Have my edits been lost? Or is there a way I can access them.
If you look at the left side of the Library view, there is a Catalog panel.
You will see Previous Import is highlighted. Lightroom automatically does this whenever you import photos: causing only those photos to be displayed in the Filmstrip.
If you click on All Photographs instead, then LR will show all the photos which have ever been imported.
Or, if you click on a given Folder, or Collection, then you will see all those photos straight away.
"Previous Import" is just one among many selective views onto your overall Library - intended, so that you can see a confirmation and (if you want) carry out management tasks on these new pictures.
Any of these views may be further filtered down in some way (such as, only those photos with a particular keyword, or whatever).
I strongly suggest viewing some kind of systematic instruction on how all this works - just to get a firm grounding. Julieanne Kost's video series on the Adobe website, for example, are excellent: very accessible (and free). If I was starting again, with what I know now, I might go straight to George Jardine's instruction series - a model of clarity and thoroughness.