Weird iPhone 4 problem

[Asura]

I very rarely plug my phone into my computer. That being said, I thought I'd look into podcasts and plugged it in today.

I'm often at the upper limit of storage on my phone, and when I plugged it in, the bar diagram in iTunes confirmed I only had around 1gb free.

It starts doing all that synching bull**** and when I come back, there's apparently over 5gb free.

Any idea what's happened? Does the iPhone have a "recycle bin" that is cleared by the sync, or something? Or is there a chance I've somehow lost a load of data?

[Mayhem]

Have you ever updated iOS over wifi on the iPhone? Could be it cleared out an old version of iOS sitting on there.

[EvilBoris]

Has it been synced on another computer before, you can only sync with one computer , so it may have got rid of a load of photos and music