sysevent runtime files are under /var/run
In 2008 this was implemented:
6711375 sysevent runtime files should be under /var/run
This changed several sysevent runtime file locations, but the manpages were not updated. At least this is no longer true in syseventd(1m):
/etc/sysevent/sysevent_door kernel to syseventd door file
The correct location for the door file is now /var/run/sysevent_door. The syseventd(1m) manpage needs an update.