I'm sure you're going nuts. I was in a similar predicament once with DH being out of town and was so anxious that we paid OOP to freeze a sample from him. In the end I didn't need it but I was biting my nails down to bone.
well if that is the case that it's only really Saturday that you can't make work then I wouldn't cancel - not yet. For an ER on Saturday you'd trigger on Thursday. And you won't be given any instructions until Thursday morning's results are in anyway so unless you need to know now, today, then I'd wait until Thursday to make a final decision.