Been a long time fellows since I have written. Been MIA on here for quite some time, but figured today be a good day to just look around. Anyway... Reaading this post there are a number of things I noticed...
1) How long did you follow her? (this seems a little weird to follow someone off a bus)
2) How did you approach her? (this can make it or break it)
3) As BuzzLogan said, should of done it on the bus. The longer you wait, the more she has time to think and the less mysterious it becomes.
A lot of times, it isn't what you ask or say to a girl, it is how you say it. There are guys who can honestly just say whatever they want and it will strike a conversation. No lie, I once asked a girl (out of being a pure joke and dare from my friends) what kind of shampoo she used. It is an odd question, but it was more of the way I asked that actually made her answer. I asked in a complete sincere innocent way. Verbal approaches are one thing, but your non-verbal language is one of the most important aspects of your game. I am not sure how you approached her after the bus. Assuming you followed her, you probably approached from the back (which is a no no). It is a threatening feeling. Approach from forward or where they can see you. This can also give you non-verbal queues on how she is perceiving you approaching.
Try this as a non-verbal exercise. It is so silly and dumb, but it actually helps and it works (with practice). I bet my friends at a bar how many "high 5's" I can get from people. I am a complete stranger to these people but I will stick out my hand and ask for a high 5 in a non verbal way. It is the dumbest thing, but the physical expression I exhibit is what lowers people's guards down and allows them to just give me a high 5. Try it out. You can easily get a number of girls to participate (I recommend asking anyone walking by, not only girls, for a high 5 because it helps with the overall non-threatening physical look of you). Also, girls will remember you and give you a high 5 when you walk by them. Easy stupid conversation starter. You can even turn it into a joke with a girl saying that you are an expert at it, or bet her you can get more than her, etc etc.
Breaking down the wall is one of the first things you need to do in order to get a girl to open up to you. Non-verbal queues play a large role in this.