When I was in the nether, I was trying to earn the achievment "Return To Sender." When I hit a fireball back to a ghast, it disappeared about a second later. I did this again, and it disappeared again. I started counting how long it took to go from the ghast's mouth to disappearing. It took about four seconds.
When I went into my creative world, I summoned in a fireball. It disappeared about four seconds later!

What I expected to happen was: To hit a fireball back at a ghast and hit it.

What actually happened was: The fireball disappeared in about a second.

Steps to reproduce:
1.Summon a fireball or find a ghast.
2.Wait four seconds after the fireball has appeared.
3.Watch it disappear!

Other:
This is important to fix because now it's really hard to get the achievment "Return To Sender", and so people who summon in fireball turrets don't have their fireballs disappear.