Awkwardly attempt to join the conversation, only to be talked over mid-sentence by someone else, and so you wait for another lull. Attempt to start again, only to be interrupted again by someone else. Watch helplessly as the subject of the conversation drifts far from the point you were going to make. Minutes pass, and everyone is glad to be talking about something else. You let go of the moment, and resign yourself to remain quiet. Then someone says to you, "Oh, what were you going to say?"
That one person is a gem and we should appreciate them. They noticed you got talked over, and made sure to circle back, noticeably so the others don't do it again, to make sure you weren't silenced. It shows they not only noticed, but were bothered by it.
Agreed, those people are the best. But also, that's a bit of a nightmare scenario, because now you have to decide if you're going to risk saying something from five minutes ago, or decline the kindness and feel bad for rejecting the gesture.