Paper-clay?

Yesterday I was having some difficulties throwing this pot.  It felt like I had an air bubble but when I tried to poke the bubble with my pin tool I realized something was actually in the clay.  So I set about trying to dig out the offending matter.  It turned out to be a large piece of cardboard. 
I had just opened this bag of clay so, even though I did wedge the clay I didn't do as through a job as I would have if the clay was being reused. I guess I learned my lesson.  I just hope Highwater doesn't charge me extra for the paper-clay.