LOST: Through a Looking Glass

I bought LOST Season 3 quite a while ago on iTunes, and was able to download and watch all of it successfully. But today, I was alerted via email that there were new episodes to download...so, I fired up iTunes and started the download. As it turns out, I simply downloaded the Season Finale (Through a Looking Glass) in two parts. I already have it downloaded as a whole, but I now also have it in two parts.

Did anyone else experience this? Anyone know why they did this?