Were they arrested and detained, or were they free to go ? What would happen to you if your country suddenly ceased exsisting -in this case, Poland and France- ? Thanks for all the answers !
Polish ambassador in Berlin was given "persona non grata" status and went with whole personnel to Denmark via train. Polish consuls were detained until it was clear that Poland let German consuls leave Poland (one consul was however for a year interned and his two deputies died in prison). Sweden was the foreign protecting power for Polish citizens till 20 November, when Germans declared that Poland ceased to exist.
Ambassadors in Poland were going where Polish government went and crossed border with Romania just like Polish government.
Soviet Union tried to detain Polish ambassador, but after personal intervention of German ambassador here who served as the most senior ambassador in Moscow (so I guess it was chivalrous - he later conspired to kill Hitler) he was let go.