In A, the instance of losing the passport happens during the process of staying at a particular hotel. So, Past Continuous is appropriate to describe this process of staying.
In B, the person is simply recounting what happened. It is similar to how Past Simple would be used in any book where a story is told. The length of visits and stays plays absolutely no role. In this situation, it's the tour itself that is a process, and it contains a sequence of simple facts.
In A, the asker presupposes that something started before Event X, was in progress at the time when Event X happened, and ended some time after the Event X. It was a continuous situation—because the asker presupposes that the guy who lost his passport (let's call him Mr. L) can pinpoint the time of loss to the time of being in a certain city. This would in fact be so if Mr. L remembered seeing his passport the day that he arrived in that city, but checked his documents on the day he was supposed to leave and found out that the passport was no longer there.
Again, this is the asker's presupposition, and this is why, coming from this assumption, the asker would apply this tense (continuous).
The answer tells us that this wasn't the case (Mr. L can't pinpoint the time of loss to a time of staying in a specific city), so Event X can't be mapped onto a time when a certain stay at a hotel was in progress, and thus we have a simple sequence of actions.