Having just ventured back to my dark past, I'm probally your non academic wanting to be a nurse pupil 4b. Did go into nursing after leaving CH and then ventured into the world of business. Never really grasped the French language and nearly caused a diplomatic incident whilst in the Pyrennes, asked an elderly man ou est la guerre, he looked blankly shrugged his shoulders and sighed. Needless to say I remembered gare and he was more animated!!! Strange organisation CH you appreciate the benefits of a classic education later in life and will always be grateful to my Mother who was a Widow for having the courage to despatch both of her children off to boarding school.
I know exactly what you mean; I have made similar boo-boos - the last one was to mix up the pronunciation of pate and patÃ© (pastry and pasta!) in the supermarket.
I doubt that you would have caused any incident - they love the fact that you try to speak French even if you do make mistakes. Mistakes made me a number of friends!
More seriously I have raised that question with lFrench friends (I live in the Pyrenees part time). To them the derniere guerre * was in the mid 1930's when several million Spaniards fled across the border and many of their descendents are still in our area. Although many local French died as guerrillas and others were deported, 1939-1945 seems less in personal memories.
*Interesting thought to get the ladies riled: why is something so unpleasant as war considered to be feminine?
(retreats to hardened bomb shelter)