If you lock yourself out why is that the problem of someone else to fix?
As the Kaba style locks require to be turned mechanically, and if the manufacturers have said it wasn't a defective lock (Phils explanation is actually the most likely) I don't know how you can argue against that. Logically they unless you get an independent inspection by a locksmith (which will cost) and providing he thinks it was defective, you could try to recover your cost via the courts (which costs) and would be in a still be in weak position. The likelihood manufacture/owner is most likely to win, and you get their cost to... see where that's all going.
Unpalatable as it may be, I wouldn't hold out much hope of re-imbursement... and make sure the key is all the way in the unlock position in future