this happened to me recently,i bought a kosta boda mine bowl from a shop in louth,me and the shopkeeper checked the bowl before i took it away and it was perfect.a bit later on my wife and i went for a coffee and i thought i would have a look at my purchase,and to my horror found two cracks in the bottom of the bowl crossing over each other,but the cracks were directley in the middle of the base and never went to the edge of the bowl.
luckily the shop owner gave me a replacement.
i put it down to the atmospheric change as the bowl went from the cabinet to being outside.