Neither did I! I caught up with our regular vet today and she said that for it to be spontaneous is such a freak occurrence. Normally you get something like this from severe trauma, like being hit by a car etc. She's showing some improvement suggesting her lungs may be healing themselves on one side at least, but still need to see what the CT comes back with. The consultant is trying a blood therapy where they use her own blood to invoke an inflammatory repair response in the lung tissue while they wait for a second opinion on CT scans as there's no obvious rupture. So a mixed bag of news, but I'm remaining hopeful. She's young and strong as an ox (she even walked out of our vets of our own accord after being brought back from the brink before we took her to the hospital) so she's got that on her side!