It could take weeks or even months before they answer you, this is a known problem within the crypto exchanges scene.

If you did a withdrawal and never received the funds (technical issue), they will be able to help you but If your account has been hacked and the money has been withdrawn without your knowledge, then Poloniex can't help you in that case.

In either case, you should be able to check your withdrawal history and see where the money was sent to.