So,
You didn't actually go to the ER, but almost did?

If you take out the ER part of the story, that leaves the appendicitis thing. Since you're not a doctor, let's take out the appendix too (no pun intended, ok maybe). That leaves:

"The no call, no show was because I had a stomach ache."

How nice of you to call all of the relevant parties afterwards to let them know!