Autofill option deleted all my previous library

As shown above, I inserted 2600 songs before I autofilled a playlist and everything was working fine (note that I had to restore my iPhone just to sync it again on my new PC). Now when I've autofilled from Circa Survive playlist, all previous music is not visible on my iPhone 4S and iTunes says most of the space is free. Wat? Only music I have available now is from this playlist.

I love iPhone sound quality which is my primary purchase reason, but iTunes issues give me headaches. This is most likely around 50th time I had to restore or delete all my music I've wasted hours putting on my iPhone.

Why does iTunes have this tendency to insist on removing complete data from user's devices? It's not like I'm gonna use iTunes to buy music anyway. And we're talking about 30 gigabytes here. That's a lot of time and effort - each time I put music on my device it's like a struggle and I feel as if I was blessed once I actually complete the process. That shouldn't be the case.

Can this data be retrieved?

If your answer is any of the following, I'm buying another device:

1. No.

2. Restore iPhone.

3. Yes, but you need to install third party software.

4. This is how syncing works.

Also, I have NO PC issues - I have a freshly updated install of Windows 8 on pretty decent desktop configuration.