I've seen the notice that the item has shipped is way after when it's actually shipped. There is often an unexplained delay there. You're making assumptions based on nothing but the timing of notices, and everyone knows those IT people are unreliable.
I've seen notices appear on the tracking page saying it was delayed, even after it displayed out for delivery. I've a feeling the tracking page is predictive rather than real time.
See if the package is marked overnight delivery, or some other rush notice. I'll bet it was shipped about Monday or Tuesday.