The Doctor claims he never gets lost, it’s just that sometimes he’s not entirely sure where he is. It’s not like it matters anyway; sooner or later he always figures out the exact where and when of their location, it’s simply a matter of taking a look around, and maybe asking the locals.
That’s the big thing, because when in doubt, you can be fairly certain that the locals can set you straight. Bound to know, if they live there, right? Besides, where’s the adventure if you always know exactly where you are when you get there? That’s just boring.