Unforeseen

uhn-for-seen (adjective) Unforeseen describes events or circumstances that happen unexpectedly without any advance warning or ability to predict them. These are situations that catch everyone off guard because they weren't part of anyone's planning, preparation, or risk assessment processes.

Think: like when your star employee suddenly wins the lottery and quits via text message from a beach in Bali — nobody saw that coming or had a backup plan ready.