As a general response to uncertainty, half-speed can have advantages. Specifically:

• This signals your uncertainty to others - someone more familiar with the area may offer to help.
• When (and if) help is offered, you are less likely to have gone too far the wrong way.

Now, neither of these were applicable in your specific hotel case - had there been anyone to ask, you could have stopped and asked, and going slowly in a car doesn't really help you. So it makes a lot of sense to ignore the default strategy in that case - and, in fact, in several other cases as well (it's a common heuristic, but it really doesn't apply in a lot of situations)