In this picture you can see how the dribble with it's thread attached fall into the mold and is quickly covered by the hotter glass from within the ladle. The hotter glass tends to re-melt the thicker part of the dribble, but the thread and it's widening drip remains fairly intact. The hotter glass softens this drip, so it does bend and conform to the shape of the mold, but it does not completely re-melt.