No, you have no reason to assume one way or the other. That means it'd be stupid to say "I don't believe you have X in your pocket, because I don't even know if you're wearing pants." Your map being blank has nothing to do with the state of the territory. If you have no more information than that, a rational agent does not say "I don't believe you." A rational agent says "I have no way of knowing; therefore, it is a 50-50 possibility."
Believing what? That I was wearing clothes at the time of that post? When I ask am I wearing clothes, yes or no, your default answer is no?
You have absolutely no basis for that opinion whatsoever. It is illogical to answer either yes or no. The answer is, you don't know and you can't know. As Xant says, the best guess you can make is that it is a 50/50 probability, which is still the same as saying you don't know, nor do you lean one way or the other.
Eh, where are my english skills to explain that...

Look, there are two kinds of questions - first kind is whether or not some fact is a fact. Like, "Does God exist?", "Do I have a pocket?". Second kind is whether or not you
think/believe some fact is a fact, like "Do you believe in God?", "Do you think I have a pocket?".
Now, the question you asked is from first category. I don't know whether or not you're wearing clothes with pocket as a fact, I just don't have any evidence, as you pointed out, so I can only answer "I don't know". BUT that still allows me to answer to a similar question of the second category - whether or not
I think you have pockets. Personally,
I do think you have some pockets (note that I still don't know if it's true), just because people usually wear some, it's a guess as Zlisch pointed out.
Now if we go back to religion. Agnostics do not say "God exists, I know it", or "God doesn't exist, I know it", they say, let me quote Xant: "you don't know and you can't know". (note that religious people usually do know there is God, same as some atheists know there is no God, they might have no evidence but at least they have something they consider as evidence).
Now let's say I'm agnostic, and I think to myself "God may exist or not, I don't know it. But it wouldn't make much sence to me if he does, the world seems to work in other ways, so I think he doesn't exists, so why would I believe in religion".
So in that sentence I state that:
1) I don't know if God exists
2) I DON'T believe in God.
I think that makes some sence.