With luck if you go into the Songs view and sort on Date Modified you will find the tracks are there, but just need information correcting. Ocassionaly when merging artists & albums iTunes gets its lists confused. Closing & reopening iTunes will normally fix that and should be tried in preference to deleberately renaming things as Unknown Artist or Unknown Album.
For tips on getting organized in iTunes see Grouping tracks into albums.
Before embarking on any major changes to your library you should backup, that way you can recover from any accidental damage.