If it was in a gas kiln, the uneven flame may be the cause on something that thin. If there is not much of a foot, the stress from slumping may has caused it. There are many variables.
All of my stuff is fired at the studio where I take classes as well (stuff I make at home I have to take there). I find it difficult to not be in control of the kilns. Sometimes a piece doesn't turn out and my teacher/owner of the studio says "Oh, that was in the kiln that didn't get up to temperature" or "That was in the kiln that underfired" or "Someone elses pot exploded". Many variables, as you know. I guess the good part is that the entire kiln load wasn't mine, just one or a few pieces ;o) So that is the upside.
I am intensely glad you mentioned this.........and what about the "that was the careless or crazy fellow student who knocked someone else's piece " (never spoken about) yes, there always is a risk in sharing a kiln. Just a question but have you noticed at your studio that anyone above mediocre tends to have more breakage? Underfired, not the right temp....somebody is watching the electric bills or not wanting to kiln sit. I just put a ad on craig's for a fellow potter with a gas kiln. I am in Denver.
I don't notice more damage among any certain people, but the turnover for the kilns is so great that I couldn't possibly know about all of the damage or kiln mishaps. We have 4 kilns and they're all fired 2-3 times a week each. I made a great piece once, and when I picked it up it had bits of bisque stuck all over the pot, embedded in the glaze. Apparently someone accidentally put greenware on the glazed shelf (maybe it had slip that made it look glazed?) and it was put in a glaze firing. It exploded. My teacher has always taught us to never get attached to a pot until the final product is in hand ;o) Anyways, I know they aren't conserving on electric bills. They have the kiln doctor come in whenever necessary. The owners are amazing. It's just like what others have said. Students still pick up other people's work even when they shouldn't.
Here's another complaint I have (if you don't mind ;o) ). The kiln shelves don't seem right to me. They are so thickly coated in kiln wash, but it's all bumpy, holey, falling off in places and uneven. Plus the dots of dripped glaze everywhere. I nearly always need to take my dremel tool to the bottom of my pots to get off either dried on kiln wash or small glaze spots that my pot was set on. Is this normal? This is my only experience with kilns, so I don't know. Oh, and the kiln posts have so much stuff stuck to the ends that they don't stand straight. I do load and unload them somethings since I work there on Fridays, so I see this all the time. I never set a pot on a drip of glaze though ;o) I normally wont even use that shelf.