The way of greeting

My University is in Kyoto. There are so many foreign tourists. I am sometimes asked how they can go to tourist spots. Last week, I was asked the directions to a famous temple in Kyoto by an American couple. I managed to tell them how they can reach there and we talked a little. At parting, they said "Arigatou(Thanks)" and joined their palms together. The day before yesterday, a French couple said to me "Konnichiwa(Hello)" to ask me the directions to a station and joined their palms together. I realised that they regarded joining their palms together as the way of Japanese greeting. You may already know, Japanese people don't do that. We generally bow as our greeting. It is when we ask a person to do something difficult, when we sincerely appreciate someone's kindness, or when we sincerely apologise to someone that we join our palms together. I was not offended by their misunderstanding, but I will explain about that if I met a person who misunderstand the way of Japanese greeting again.