I'm not sure if it happened but I can say that much of Hemingway's world war 2 experiences are up for debate.

This comes down to two main factors, his telling of tall tails/exaggerations and also that being a war correspondent he shouldn't have been participating in combat.

The story is often mentioned by journalists, which keeps it alive. It is mentioned in A Historical Guide to Ernest Hemingway by Linda Wagner-Martin (pp42). Otherwise I don't have access to better sources.

If possible you should read Correspondent or Warrior?: Hemingway's Murky World War II "Combat" Experience, William E. Coté, The Hemingway Review Volume 22, Number 1, Fall 2002 pp. 88-104

Anyways, the reason I posted was that I thought you might like, if you are a Hemingway fan, the online copies of his reporting during the war. They make no mention of the 'liberation'.