Hello @Alle2142 and a very warm welcome to the Community Forum. I am sorry to hear this, was this a confirmed sit? Also, just to check, have you now re-listed your sit?
You can also add your TrustedHousesitters profile on to your Forum profile on here by following the attached link, should you wish. This will then enable others to offer you helpful advice and feedback for your listing as well as giving it extra exposure.
Please try not to worry, mid December is still quite a way off and you have plenty of time still to find a suitable sitter/s. 