Yes apologies, I found countless mailing list entires that seem to indicate scanning for access points is.. flaky.. and that the interface needs to be up for it to work on NetBSD.
I'm pretty sure that
wiconfig(8) is for a specific family of wireless drivers, but perhaps the following might work?
# wiconfig wpi0 -D
If it does not work, perhaps you should file a bug report.. or.. send an email to their mailing lists.
One reference on NetBSD's "tech-net" list indicates that
net/kismet can be used to scan for access points.
http://mail-index.netbsd.org/tech-ne...msg001046.html
Ironically the topic is about how broken ifconfig+list+scan is.
Hope that helps.