Jupiter-mass planet named WASP-17 discovered; has odd retrograde orbit around its star

The discovery of an interesting planet was announced today and you can read about it here. The planet is 1000 light years away and not only has a retrograde orbit but is also twice the size of Jupiter even though it only has the same mass. To see how a retrograde orbit looks compared with more "normal" orbits, see the link at this post where you can follow along with an asteroid that also rotates in the opposite direction of the Sun. As you can see from this list here, retrograde objects really aren't that common.

Apparently the running theory is that this orbit may have been caused by an impact. Could it have also been a planet captured by the star? After all, the moon Triton also has a retrograde orbit and is thought to have been captured from the Kuiper Belt.