Losing Purchased Music and TV Shows

MAC PRO Retina Early 2013 O X Mavericks Latest iTunes installed

Lately I have have been noticing that some of my iTunes Store Purchased songs (~10) and some TV series (3 Castles) that I have downloaded, played on my MAC and Apple TV and shared with my iPADs/iPhone/Nano/iPod are no longer showing up in my Library anymore and the actual files have disappeared from my MAC. The first indications of this was when "synching" with my devices and having the songs/TV shows be "not found". Also, when using a iPad that I had successfully transferred a copy of the TV show to, it somehow disappeard from the iPAD (latest iPAD AIR model). All my tunes/movies/shows in my MAC Library are all located on the internal drive in the usual place (not spread all over the disk, etc).

I have searched the disk end to end for the "missing" actual tunes/shows files and they are no longer on my computer at all. They are even missing from my recent iTunes backups.

When I go to the "Purchased" list on iTUNES, the songs are not listed among the other ones I have purchased so I cannot "download" them again. But the TV shows are there for me to download AGAIN (and AGAIN, and AGAIN, etc.) I am only running them on Three AUTHORIZED computers and have been an iTunes user for over 4 years.

Going to the iTunes Library on one of my PCs, I can transfer the missing songs/Shows back to my MAC, but within a day or two, they disappear again.

This is very frustrating as I have paid for these songs and for the TV series and they keep disappearing from my possession.