Question in title. All them seem to be heavily damaged but with half surviving at least. Cant find any that were wiped out.
If you mean a "heavy bomber flight" being one that was completely destroyed, then yes... And it happens to be a very famous one...
The Dolittle Raid consisted of 16 bombers that bombed Tokyo on April 18, 1942. All but 1 of the original 16 aircraft crashed in China, with one landing in Russia.
Yes there undoubtedly has been, at least if you are willing allow that the concept of a "strategic bomber" may include a world-war-two-era twin-engine bomber attempting to accomplish a strategic objective. I'm thinking of some of the early RAF raids carried out by bombers such as Hampdens or Whitworths or similar, or raids by the French before their surrender.
The answer to most "has there ever been" questions is "yes".
Admittedly this answer is short on actual details/ examples, and could be improved.