I've read on here also from other experienced YT'ers that often if your puppy's tummy is empty for a long period of time (overnight) they can throw up a yellow bile. This may be what it was.
As for "over reacting" to her spay....nope, not at all.
I did the exact same thing. I tried to stay calm and cool when I dropped Sophie off for her spay (back in March) as I didn't want her to pick up on my nervousness. But as soon as I walked out of the office I cried all the way to my car and the whole drive to work. I was a mess at work all morning and couldn't think straight with worry. The Vet called around 1:00 to say all went well and she was waking up and giving kisses.
I had all the tests in the world performed on her BEFORE surgery....all the necessary and optional ones! LOL I was so scared!
Any word yet from the Vet?