Password? What password?

This morning I mindlessly did an iOS upgrade -- I came into work, plugged my iPhone to charge it; iTunes popped up and prompted me to do some upgrade. I haven't had my morning coffee yet, so I just clicked OK. When I realized it was upgrading my phone, the process was already well under way. So I decided to let it go ahead -- I am now regretting that (non-)decision.

I was working on my PC doing whatever I was supposed to do. Then this screen popped up:

I thought, hmmm.... What does that mean? Was the upgrade completed? Or did it fail?

At that point, it didn't seem that there was anything else I could do. So, I went along. Then I got this:

That made me a bit nervous. If this warning came earlier, I might have stopped the upgrade even not being fully awake. But at this point, what could I do? So I hit Restore and Update.

Now that's strange! I didn't see it doing the backup. So I definitely did not set a password on the backup. I tried my Apple account password, my Windows password, etc. It just kept giving me the same password ... was incorrect message.

So I googled iPhone upgrade backup password. This one came up on top of the result:

To put it mildly, I have never liked Apple products. Now this is pushing my dislike to a level of hatred.