I accidentally left a pyrex pan in the oven when I baked bread this afternoon. So, basically, you had an empty pan roasting at 400 degrees for 40 minutes.
Is this a problem?
It looks OK, and I left it in the oven to cool down slowly on its own before moving it. It’s intended for baking in the oven, it’s just that it was entirely empty.
I wouldn’t expect it would be an issue. There’s no coating to be damaged like on a non-stick pan, and you didn’t superheat it, or subject to any kind of temperature shock, so I can’t really think of anything that could really be wrong with it.
I’ve done this to my pyrexes a couple of times. They don’t seem damaged in any way. The pyrex page has a link to a pdf with customer service numbers at the bottom, if you are worried enough to call.
Pyrex was designed for laboratory use; labs do much worse things than simply heat things to 400 degrees. Set them atop Bunsen burners, for a start. Or use them as the staging area for nasty chemical reactions.
You did the right thing by letting the pan cool in the oven. It would probably have survived being removed (it survives being removed when it’s full of food, after all), but it was as well not to take the chance. Even laboratory glassware sometimes doesn’t survive temperature changes, and it’s thinner and more resilient than the stuff for home use.