If the Genius told you that the moisture sensors had activated enough to void the warranty, I would think that more than a couple of drops hit the thing. The iPad screen is fairly well sealed. There is a moisture sensor in the headphone jack, like on the iPhone (as well as in other places). But it needs quite a bit of moisture, I've heard, in order to turn completely red (the indication). But I'm surprised that he told you that all you could do was throw it away! You mentioned that the screen had not been working well before this. What, exactly, was not working well about it? Did you tell that to the rep?
If indeed you managed to void your warranty, look around for iPad repairers who work independently (there are quite a few fixing iPhones, so maybe start with them). Maybe they can repair it and if so it would cost a lot less than the out of warranty repair from Apple.