2010 oil change diy disaster!!

That's 1/2 true. Fortunately (for the consumer) the half you like is true. The dealer would probably have to eat the engine.
However (I'll skip the comma this time) even though I'm a noob to the land of Prius, I suspect that there's an "idiot" light that will inform you that there's something amiss in the lubrication department.
Priuses have 5 different ways to tell you how much gas you're using, but no oil pressure gauge. Go figure.
If your oil pressure light illuminates, and you do what you're SUPPOSED to do---shut down immediately and diagnose, then in the case of the ruptured formed seal (gasket) you've successfully detected a problem before it becomes overly damaging to your engine.
Qucik trip back to the garage and everybody is happy.
If you're like MOST drivers who never check their oil,and the leak manifests itself over a looooooong period of time during which you never checked your oil level, or noticed any leaks, and months go by with our little engine hero operating under a slowly diminishing supply of increasingly overused oil---then yeah, you're gonna damage your engine. The mechanic is the root cause, but is it really ALL his or her fault?
Dads used to give a lot of silly advise back in the day when a 6-litre engine got 10 MPG and produced 120-BHP, but one thing that he always said still holds true today....

Check yer oil!