Sometimes, the signs are not clear, sometimes, it's in a grey area. Feelings can fade, but it can also develop. It usually does not seem conspicuous initially, but if you take a step back and look, it then will start to look more apparent. But, that does not mean that what has been thought is what's happening.
For one person, it really seems like friends. But to that person, it may not seem like it. If someone can say that they may have feelings involved, then it may or may not be true.
Anyway, girls love to friendzone guys or vice versa, and it's a fact. There are a few type of guys that have always been friend zoned. The nice guys, or sweet girls for that matter. The guys or girls that have always been there for you, from your darkest days to the brightest days. You have just appeared to be too available, which is also the cause of the friend zone stigma. Also, he or she is there when you need someone to listen to your sad sappy stories, your heartbreaks or even some love advises.
When you're being friend zoned, it's sad news. It means that the probability for that person to reciprocate is just low unless you detach yourself from being friend zoned. Sometimes, it cannot be avoided and sometimes, people manage to pull themselves out from the platonic relationships. You just gotta know when to pull back I guess.
Personally, I have friend zoned quite a number too hehe. It all comes so naturally. It cannot be otherwise.