This is probably a little late (sorry if being redundant), but here are some diggings on the missile:

Blogs on it shortly afterwards:

https://www.thedrive.com/the-war-zone/21461/lets-talk-about-that-mysterious-rocket-launch-over-whidbey-island-photo-from-washington

https://cliffmass.blogspot.com/2018/06/was-there-unannounced-missile-launch-on.html

Time lapse of feed that night:

https://www.skunkbayweather.com/WhidbeyMissile.mp4

Some twitter pics too of some conversations that took place on @skunkbayweather.