Manager - Not giving any Feedback?

So I had to find out through extra-managerial channel and officeroom chatter that my contract as a Graduate Extern is not being renewed at a Nonprofit. During my midterm review, I was given stellar remarks and comments and my manager told my project coordinator that she wanted me on for another year. While I haven't yet met with her to discuss this (it's happening monday) when I asked her, just in passing, if she'd write me a reference and followed it up with "So I've been meeting your expectations?," her face fell a little bit and she said "well, kind of. We'll talk about it next week." At first I didn't think much of it, but I just had confirmation from my program coordinator that "There have been new developments since your midyear review." Again, I had to seek this information out. In terms of my performance, I was never given a formal sitdown session once about my performance. The worst offenses I could have been accused of was maybe writing an e-mail to my program coordinator using my e-mail account or listening to music while I did boring data entry. Beyond making a few small humorously-toned chidings, she never really ever communicated with me directly that my performance wasn't what she wanted. So when I found out my contract wasn't getting renewed, I was floored. I was more floored given that they don't pay me a red cent. My school does. I'm free labor to them. I just find it astounding that I'm being punished for behavior (which I don't really know what was so egregious?) which was never expressly forbidden to me and which I was never really given feedback, concrete, direct, behind closed doors, a serious-talk-to-talk. Not even a written reprimand. What gives? Part of me is really furious.