Won game revoked from my account

Contact the giveaway creator, yes.

Contact giveway creator and ask if he can provide a replacement key. If not you can either be a good sport and agree to giveaway deletion or ask support to change your win to not received.

Do these steps in order:

1. Contact support and ask to change the win to not received
2. Contact the giveaway creator and ask for a replacement key

If a key is provided then you mark the giveaway back as received, else you carry on.

If it's a giveaway old enough that you can no longer mark it as not received then go ahead and contact the creator and write to support asking to mark it as not received ASAP. I once got suspended even tho I had done both things because the suspension got processed much faster than my ticket to support, so don't make the mistake of trying to be nice about it and waiting for the creator's response.