You do not need to ask CS about this.
It's tracking which is important here. On your delivery order is there any tracking? If it shows delivery then you will not be able to claim any refund through eBay's 30 day MBG Money Back Guarantee . Ask your seller too, to provide that tracking.
If they cannot, then open a case for item not received, this can be done one day after the item's last estimated date for delivery . Escalate on day 4, if not refunded beforehand.
Be aware, not all couriers ring doorbells, ringing a bell means they have to wait for someone to open the door, some are on a tight schedule to deliver X amount of items, so they just leave items and go. Some are left in unsafe places, and yes they can get stolen.
@chris24781
