I had a similar experience with my Smudge who I had pts in Jan 05.
Smudge was my first cat, the light in my life and forever number one in my heart.
Aged 15, after 6 weeks illness, he was finally diagnosed with a particularly aggressive form of cancer.
My world turned upside down.
He was given a strong painkiller to see him through the weekend, so my ex-husband could visit to say his final goodbyes.
On Tuesday, 18th January at 12 noon, the vet who had seen him through his illness, came to relieve him of his pain, I was incredibly brave & composed, the vet left.
We were warned it might look like he was breathing for a while, we sat talking to him, telling him how much he was loved and stroked his body, we did this for some time, for almost 2 hours, when my boyfriend finally said: 'he is still breathing you know'.
We had to ring the vets, the vet came out again to administer another injection, into the heart, I flipped, I was a wailing wreck.
I've never mentioned this to my Ex, it would have been far too distressing for him, or my parents.
I have only ever mentioned it to the lady who runs the local CP, as I have had to avoid this vets practice.
I know I should have complained, I never even got an apology, but I haven't been able to put this is in writing until now.
Despite this, two weeks after, I re-homed a 13 year old stray.
His name was Reg and as many of you will have read, I had to have him pts a few weeks ago, almost 2 years to the day.
In a way, Smudge has also been laid to rest properly, as he should have been too.
My heart goes out to your guests Mark.