My pipe blew in the exact same spot on the way home from picking up my F, so I thought I would cut it up after reading this to see if mine was the same. Here are my findings...
My hose blew out in the exact same spot as David's... Same symptoms.. Steam etc. (unsurprisingly!)
Pipe was almost completely blocked.
Closer view from different angles
To me, it looks like it should sit like this in the pipe
Looking at the piece that came out, it looks like it has been glued in place originally but over time with the heat and pressure it must weaken the glue and let the piece move out of it's place.
My piece moved up as far as it could and had rotated 90 degrees to almost block the pipe completely
Here is the offending article.
Looks like it may be worth MGF owners giving this pipe a squeeze to make sure this piece of plastic has come unstuck from where it is supposed to be and blocks the water flow.