You did absolutely the right thing by going to hospital with a raised temperature and it has proved to be fully justified with that diagnosis. That is a lesson for all of us.
As I said earlier in your thread, I ended up in A&E twice during my first chemo cycle. The first time was because we were being overcautious, with only a slightly raised temperature ( I think it was just touching 38), but the second time, about 3 days later my temperature was 39.
On both occasions, the A&E treated me immediately for sepsis, with antibiotic drip and lots of blood tests. On the second occasion, my neutrapena count was very low (or was it high, I can't remember now? It was a long way off what it should have been anyway). But I didn't actually have sepsis. They let me go home the next day, but I had to go back every day for 3 days for tests, by which time the neutropenia had started to normalise.
However, I had 5 more cycles of Docetaxel after that, without any repeat of the high temperature, so don't worry too much that it may happen again.
I understand the feeling of shock you had, but all's well that ends well. I am glad he is feeling better today and long may that continue.
Best wishes to you both