Hi Christoph,
Sorry to hear about the fur shot. As has been advised above, in such circumstances you never know whether some insulin was delivered. My vets always warned me that if I had a hiccup when giving an injection to always wait until the next dose was due. When I wasn't sure about a particular injection, I would keep an even closer eye on Saoirse during that cycle. If anything looked unusual, I'd give my vets a call to run any concerns I had past them.