it evaporated into the mists of coincidence

Evaporation: liquid water - vapour
Condensation: vapour - liquid (water droplets around particulate matter in the air like dust)
Precipitation: suspended water droplets in atmosphere (from cloud) - liquid or solid water forms onto the ground (onto land)

There wouldn't be a mist without condensation and we couldn't get condensation without evaporated vapour settling around condensation particles. It is cyclical.

So, the part about something evaporating into a mist seems to me to be both semantically and scientifically correct.

However, I am uncomfortable with the 'mists of coincidence' part. I understand the metaphorical sense of 'mists' as, alluding to qualities that obscure, blur, confuse; anything that evades clarity. Maybe even ephemeral. Its meretricious quality seems less likely to be the metaphorical element.

A coincidence is an event; it is an occurence. It might evade understanding; we might view it as esoteric and imbue it with symbolism, but none of this makes it 'misty'.

Still, there is always the matter of artistic license, I suppose.