Audio problem: Before the famous attack by a crop spraying aircraft, Cary Grant is set down in the middle of nowhere from a Greyhound Scenicruiser. Another bus, a Flxible BR-29, also stops briefly. The soundtrack of the Scenicruiser's engine is re-used for the Flxible.
Audio problem: Near the end of the movie when Cary Grant says, "Come along Mrs. Thornhill." If you read lips he's actually saying, "That's it." (02:15:45)
Audio problem: When Thornhill and Kendall reunite after the shooting, they are obviously on a soundstage and not on location in the wilderness. There is absolutely no background noise, which is impossible in the outdoors: leaves rustling, birds calling, water trickling, wind gusting, etc. prevent the complete silence depicted by the movie. The quality of the actors' voices also sounds like indoors rather than an open space. (01:46:30)
Audio problem: When Thornhill and Kendal are having dinner on the train, at one point Kendal says "I never discuss love on an empty stomach". Watch her lips and you'll see that Evas Marie-Saint is actually saying "I never make love on an empty stomach". The scene was clearly redubbed.
Answer: Not really. You could (and at some hotels are still able to) keep your room number private or you could not - i.e. you could ask the hotel staff to keep your number secret from strangers, or you could ask them to tell anyone who might ask. Not having seen this movie, I don't know how likely it would be in the situations you speak of that the hotel guest would choose the latter option- it might be a mistake.
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