I guess if the clay is 'thick' enough where it broke, you could 'bore' into the 2 broken surfaces and use something to 'connect' the 2 pieces. But if it's a crack at a relatively thin part of the figuring, I think you're out of luck. In either case, no matter what you do, I have the feeling that you will see the crack.
Maybe others have have some ideas. My best to ya and hope this helps.
PS: After this afternoon, I won't be back until Monday 9/18 but 'others' will be around ...