My favorite thing to get at subway while still watching what I eat is a six inch veggie on wheat with a little oil and vinegar. I'm VERY particular about how much oil, too. (That is... not a lot) It comes out to about 7 points.
You say you're looking for a zero point snack. Are you using all of your servings of veggies and fruits in between? They can certainly be filling.
As far as that baked chicken sandwich... do you mean
This one?
For the info they give on the site it comes out to 11 points for the 6 inch.
The one thing I really appreciate about Subway is that their nutritional information is all over the place. They're very up front about it, so when I do go there I can make a very informed decision.