You searched for: “causimomancy
causimomancy, causinomancy (s) (noun) (no pl)
Prophecy by the action of objects placed in a fire: Greg watched the old chair going up in flames, and wondered, by the method of causimomancy, if he would have luck in finding a new job.

Considered erroneously, “it is a happy presage when combustible objects don’t burn when thrown into the fire”. This was considered a good omen if something failed to burn or took a long time to catch on fire.