Glitched Snowball! Need Help!

I am currently doing frostmaw's, and i am stuck on the third level. The snowball at the end of the level that u need to break down the gate is not moving. It is just staying still where it usually starts at. does anyone have any ideas of why this happened or how to fix it without having to start the whole dungeon over?

Use the Blast keg if the Snowball is stuck. It's found back a ways near an area map.