Didn't get 20,000 gems

It'll probably come out someday. I don't know when that 'someday' will be, but it's obvious it'll drop to 500 gems once it's out anyway.

If it hasn't disappeared, it might go up, but if it has, aim for the next one. That's a shame.

Even if it's not 20,000 gems, 18,900 gems is still a lot! If it hasn't disappeared yet, keep trying now. You never know when it might vanish.

I keep getting only 500 gems, I wonder when they'll give us 20,000!!

It sometimes stops for a bit and then suddenly spikes up, so keep an eye on it. That happens to me sometimes too.