Has there ever been a strategic bomber raid completely 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. 


Source: Wikimedia