Hi Sam,
You may be dealing with someone who is really shy.
They look away when you turn to stare back at them because they may be very worried about making eye contact with you.
A shy person would worry about being caught staring.
Hence, they look away.
When you decided to say hi to this person, they most likely didn’t reply because they may have worried that you only gave them this kind of attention because you knew that they had been staring at you for a while.
A shy person can get easily embarrassed when found out.
Hence, they may not have replied so as to avoid putting themselves in an awkward position where they may have to acknowledge that they have been constantly staring at you.
You have noticed this person again in your neighborhood.
This time, staring at you with a glowing happy face.
They may still want your attention.
However, you may have to approach them in a totally different way in order to be more effective.
If you know the path that they tend to take, you could physically put yourself on that path.
This way, you are literally going to bump into them.
This is when you will have the best shot at getting the person’s attention.
As the person arrives, you could briefly stop them by complimenting something that they may be wearing and then proceeding to identify with it in some way.
For example, the person may be wearing a t-shirt with some interesting lettering or even symbols.
You could comment on it and relate to it by mentioning something that you have in common with it.
This will put this person in a position where they will feel a lot more comfortable replying, as opposed to ignoring you as they did the last time that you tried approaching them.
From here, you may be able to get a better idea of what this person is all about as the conversation progresses into other topics.