Logic board damage - could this be anything other than liquid damage?

Hello, everyone. I'm a first-time poster, and very grateful for the collective wisdom on offer.

I bought my Macbook Air in Canada in October 2013, and whisked it off to India for a nine-month research trip.

About three months ago, while still in India, the unit stopped charging: it could hold its charge if plugged in, but the green/orange mag-light would never turn on. We gradually lost charge over three months, until, stuck at 0% battery, the computer would often turn off randomly, even when plugged in. It finally fizzled in the archive one day, with one sad little puff of smoke.

Upon returning to Canada, I dropped off the Air at a MacStation Store, and they've just sent the following photos (posted below), alleging liquid damage and denying the warranty. I'm completely sure that we never spilled anything on it, and, on the day it smoked and died, I was even in a State Archive, where liquids of any sort are strictly prohibited.

I feel like MacStation are accusing me of dishonesty, and, this being my first Mac, I'd expected (and heard of) better support. Can anyone think of any alternate explanation for the damage? Looking at the circuit board, where has this damage occurred? Under the keyboard, or?

The climatic conditions became humid in India as monsoon arrived and archives were often dusty, but I can't think of anything that would create what looks, to my untrained eye, like concentrated and highly acidic corrosion. My cursory snoop around online suggested that the mini, white disk in the upper-left of the topmost image is a liquid sensor: does the fact that it remains white (rather than proof-of-liquid-damage red) help my case? Could the battery itself be involved here somehow, with the mag-light/charging backstory in mind?

Any wisdom on what's going on here, or how I should proceed, would be incredibly welcome.

Many thanks!