If choosing to disable the Notification Center toggle for an iOS app, does this mean that notifications can't be located after they've disappeared?
What that switch does is reject the push from the server. One message might still get delivered if the server side doesn’t receive the message but the device send back a “we’re not subscribed anymore” message until you re-enable notifications.

Notifications can come from apps on the device or from the Apple Push Notification Service - so either way - those messages literally are stopped and discarded as opposed for them all to keep piling up and not being visible.