UPDATE: I think it's the SD card. I just noticed that when pressing down on the sd card, you can actually see liquid moving inside the plastic. If the fumes let off by the banana were insidious enough to do THAT, then at least some other part of my device would have been wet as well. But it was just the sd card/slot.

I've contacted the seller through amazon. I threatened to get amazon involved, and to leave negative feedback. Any other advice on how to proceed from here??