Missing purchased music

If the tracks are still listed in the Music part of your Mac's iTunes library (even if the music files themselves are no longer on your Mac) then 'transfer purchases' won't copy them back from your phone - that will only copy those purchases that are no longer listed in your Mac's library.

If you can re-download songs on your phone (music can't be re-downloaded in all countries) then you should also be able to re-download them on your Mac's iTunes via the Purchased link under Quicklinks on the right-hand side of the iTunes store home page - but similarly they will show as 'downloaded' if they are still listed in the Music part of your library, they will only get the cloud symbol for re-downloading if you delete them from there.

If you aren't in a country where music can be re-downloaded, and if they are still in the store, then you can try contacting iTunes Support and see if they will grant you a re-download : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption

Do you get the Purchased link on the right-hand side of the store home page under Quicklinks, and if so what types of item do you see there ? The types of content that show will depend upon what country that you are in - this page lists what can be re-downloaded in each country : http://support.apple.com/kb/HT5085

If they show as 'downloaded' then are they still listed in the Music part of your library i.e. where you could normally click on them to play them on your computer ?

If it says 'downloaded' next to them when you go to the Purchased link under Quicklinks then are they still listed in the Music part of your iTunes library i.e. where you would normally click on them to play them in your iTunes library ? If they are, then even though you may not have the actual files for them, iTunes is seeing those entries in your library and is assuming that you have them somewhere and that there is no need to be able to re-download them - try deleting one of those 'entries' from your iTunes library and the 'downloaded' for it should then change to a cloud symbol on the Purchased link allowing you to re-download it.

You should be able to find where a particular track (or film or tv programme etc) is stored on your computer by control-clicking it in your library and selecting 'show in finder' on the popup that you get.

Or you can go into Preferences in iTunes (command-comma), and on the Advanced tab on that should be the 'iTunes Media Folder Location'.