Just to update. I was able to get my coins. Kucoin support was helpful and timely in assisting me.
I also changed the title of this thread from "Kucoin stole my Polymath?" to "Kucoin delisted Polymath", because the first one may imply deceit.
Congratulations for you able to get your coins, look like Kucoin support is not bad, according their blog post
Withdrawals of relative tokens from KuCoin will continue to be supported until 18:00 (UTC+8) on May 03, 2019.
Actually they have the right to ignore you, but they won't do that and still assisting you, it's good. Next time double check spam folder to make sure don't miss any important email.