Earlier this year I broke the above piece on my Bigshot in a similar manner as Sussanna did. I contacted Sizzix to find out if I could purchase a replacement for this bit, which they then offered to replace free of charge. I had to wait quite some time as the part was ordered from America but it was worth the wait. So the lesson to this story is simple be careful not to make you sandwich to big and if you did know who to call:)
Big thank you to Sizzix for excellant customer service and support.