First off I want to say that I actually agree there is something fishy here, but I don't think where you are looking.

I do think the F-35 gets a bit more hype than is warranted, largely because they have to recoup the price by selling to foreign allies. Issues often get swept under the rug, downplayed or are distracted by other stories like this.

That said, I can think of dozens of reasons a pilot might eject and somehow the jet continues on autopilot for 70 miles. He doesn't have the benefit of knowing it's about to make it another 70 miles. It might look like it's about to fail eminently and then miraculously doesn't. Sensors could be indicating something worse than reality or perhaps the plane just miraculously lasted longer than it should have.

My car drove at least 800 miles last year while my engine mounts had completely rusted out. I had no idea except a bunch of warning lights that came on about 600 miles into it. It's a miracle my engine didn't just slip out, but somehow it just rested on the shocks and kept me going for way longer than my mechanic would have ever thought possible. Real life doesn't behave exactly the way you expect no matter how much you look at the data. Sometimes a stray spark causes a massive wildfire in a damp and rainy season, sometimes an entire box of matches wont start your expertly built campfire.

I find the story itself plenty believable, it's just the plane itself I don't trust. The "cutting edge" F-35 Lightning II is remarkably susceptible to electronic and electrical warfare. That last bit is a dig at how it apparently can't fly during lightning storms. You heard that right. It's called the Lightning II and it absolutely shits the bed in a lightning strike.