It's expected after any major update that some settings might be shifted around. For Windows 10 users, the release of the Anniversary Update today has reset their Pen settings. But that's no reason to worry since forum moderator Greg over at Microsoft Community has made a statement already:
We are aware of an issue that could reset a few personalized settings choices to their defaults during the upgrade to Windows 10 Anniversary update. The Windows team is working hard to fix this as soon as possible. Please go to Settings > Devices > Pen & Windows Ink to re-personalize your pen settings.
Prior defaults were:
Click Once -> OneNote universal
Double-click -> Send screenshot to OneNote universal
Press and hold -> Cortana
The issue is a minor inconvenience, but one that Microsoft is already working on correcting. As the day continues, we'll certainly hear more about other bugs cropping up from the Windows 10 Anniversary Update. But in this case, the features outweigh the time spent adjusting the settings once more.