Honesty of advisor when determining an adequate research project for thesis
I would like to start by reinstating an already made comment: it is hard for anybody to look at this kind of mild conflicts without biases. The student who replaced you certainly had to replicate some of the work you have done, and most likely has been exploring and wandering in other research direction. 

That being said...welcome to the academic world. Not all advisors are able to mediate their own best interest, with their students/postdocs best interests. Let me be more precise, and talk in economic behavioural terms: it is always the advisor's best interest to get as much work as possible from any person working for him. He/she lives in a highly competitive world battling with few resources to stay ahead of the competition. However, any supervisor needs to balance his/her need to get the most work out of his/her research group, with the need to build a positive reputation in offering a working environment that compromises reasonably between being treated fairly, and having the opportunity to grow in a career while working hard. Failure to do so will cut his/her stream of future students/postdocs into his/her group. 

It seems like your advisor did not quite strike that balance - especially about the unpaid work. Unfortunately, that too is all quite common, especially in universities/countries where funds are lower than in the average US institution.
Just take it as a learning experience, and try to learn the most out of it.