I second derik.pfeffer's recommendation for using a custom property field on the node (or disk, interface etc.) for storing the details. Alerts in the active alerts view are transient and, once the alert has been cleared by the alert reset conditions, whether the alert has been acknowledged or not, the alert is no longer visible in that view.
How do you do your notifications of alerts? If you use something like email you can send an alert trigger email with a link that allows you to acknowledge the alert with a single click (provided the system you are on has access to the Orion web console). You simply need to send the variable ${AcknowledgeURL} in the email or other alert action for someone to click on. Their credentials will be dropped into the Acknowledged By field as well. Great for active alert management.