A Post without a Picture?

It seems to me wrong to post without a picture,
but i had a weird occurrence the other day, (for the second time) that i couldn't figure out, and couldn't chalk up to some freak occurrence again.
Keep in mind that this is the second time this has happened:
I have experienced, and can logically understand why, when mixing clay, the clay actually heats up (warms) if it mixes for a longer period due to the friction of the matter moving and rubbing against itself in the hopper. Similarly, I know that microwave ovens generate heat by causing the water molecules in the to-be-heated item to rub together causing friction heat. I've also heard that clay warming through the mixing process is not a good thing, as the warmth kills off the good bacteria that lend to the clays plasticity.
This i can understand.
The other day, I was mixing clay in my classroom, using a peter pugger, and i reached in to dislodge some clay that wasn't blending enough, and when i touched it, i was surprized to find that it felt like someone put ice cubes in the barrel. I was so surprized. The clay itself was freezing cold, but only a little cold patch mixed in with all the other regularly temperatured clay.
I have no idea how this could happen, all the clay is store in my classroom, so it's not coming from outside.
I speculated that maybe a student actually put ice in the machine, but i really really don't think that that is the case.
Is there some way that this can happen chemically through the process of mixing?
i'd love to figure this out. Maybe i'll go and talk to a science teacher and post my findings if any.
If anyone has thoughts or knows the answer, i'd love a reply.