Well, we are--by email. And I'd imagine the vast majority of alerts do get seen and read by moderators. However, there is an equal possibility that they missed the email as there is that they saw your alert and decided it wasn't something that needed to be acted on. Either way, if you want a response, your best bet is to send another alert. (You may want to mention apologies for the duplicate alert but that you hadn't seen action taken and hadn't received a response, so you thought maybe the previous alert had been missed.)