I hope you and Wookie don't mind me answering your question.
Rule 5:
"Every Vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and the risk of collision."
As I have stated before I am a has-been; a former professional mariner.
Things change; however, I am not aware of a waiver to Rule 5 for anchored vessels in the International Rules of the Road.
Therefore, a competent anchor watch mate should hear or possibly see by vision or interpret for sure by radar, that an approaching vessel may cause a collision.
Conception is a small vessel. It is only about 75 or 80 feet. A lone mate while following Rule 5, should be able to detect smoke, heat, or fire relatively quickly. Did the fire propagate to an inferno in less than a minute? I don't know.
markm