How can we prevent this from happening again?

Prevention is better   than cure! To avoid reliving this scenario, a few  simple actions  can make all the difference:

•  Lubricate the lock  regularly with a suitable spray  (avoid classic oil which can  clog  the mechanism).
• Check the condition of your keys : a worn or bent  key   is more likely to break.
• Protect your locks  from temperature variations which can affect their proper functioning.

Proper  maintenance of your locks  can help you avoid many problems. And if  your key breaks again , you will now have the  right reflexes  to recover it  without stress  !