When you are one of the top 3 or 4 donators (depending on the wonder) you get a reward. To get rune shards for the same wonder, you have to be the top donator. For all other reward levels, it's a small number of KP. So you may have got some KP back, but may not have noticed. I know sometimes the game has a pop-up letting you know that you were one of the top and sometimes it doesn't.