I did report it, and Julia from Customer Support has responded:
“Thank you for reaching out to us! Regarding the missing devices, after we had made the changes from our end the devices were temporarily removed so that Sense can re-learn them with a newer, more accurate set of data and prevent confusion between the other devices. As this is the case, the dryer should reappear in the list of devices after about 10-15 days. If the dryer doesn’t reappear, it is possible that Sense just needs some more time to re-learn the dryer in your home. However, if this happens please be sure to reach out to us so that we can look further into this. I apologize for the inconvenience, and if you have any questions or concerns please let me know!”
I believe the “changes made” were in response to an earlier ticket that I opened regarding confusion between devices. So you’re right, it is not firmware related. Probably just a coincidence that this happened on firmware update day.