Hardened nozzle tip broke off during printing  

Hardened nozzle tip broke off during printing

I was printing a rather mundane PETG print earlier today, one I've printed plenty of times before, and I watch keeping an eye on the camera as the print was almost completed.

But then I see the print sheet being slid and lifted off the heat bed, with the print stuck to both the nozzle and the heatbed.

I stopped the print as quickly as I could, and started removing the PETG blob that had started to form around the nozzle, which was easy enough, since the plastic was still hot. However, that's when I noticed that this wasn't a normal blob of nozzle snot: The actual tip of the nozzle was missing, causing the extruded PETG to come out in a shape similar to that of toothpaste.

I wish I knew where the tip went - I probably lost it down the drain in this repurposed bathroom, as I wasn't aware of it being AWOL when I removed the print and printsheet. It's not in the print, and it isn't in the printer.

I've now changed back to the original brass nozzle that came with the printer, and it's printing just fine.
Any chance this is a manufacturing defect in the nozzle? It was a Prusa Hardened Nozzle (Nickel plated) 0.4mm, and I've been using it for less than a month (Part of Order No. 1764450524). I've had no issues with it until now, and it was in good condition and hasn't experienced anything that would've damaged it.
Either way I'd love some insight into what could've happened, so that I can prevent this from happening in the future.