This is going to be hard because I don't know many details about it:

-It was composed by Motoi Sakuraba.

-It sounds VERY similar to the song "Motion" from Sakuraba's Gikyokuonsou soundtrack.

-Pretty sure the only insturments are piano and drums, like the song I mentioned above.

-Sounds like a battle theme; fast rhythm and melancholy.

Have you listened to that entire album? I did a quick search on Youtube of the album and several of the songs on it sound similar to "Motion". Actually, now that I have been listening, a lot of his battle themes sound very similar to each other... I don't have much free time right now, so I can't really look as much as I would like. So, why not just look up the battle themes to his games (Baten Kaitos series, Tales series, Star Ocean series, etc...) and see if any of them match up with what you want. When I get some more free time, I can try looking again. Good luck in the mean time.

Hard to say. Oddly enough in the games Sakuraba composes there are actually very few piano focussed tracks used in battles or similarly urgent settings. Some examples I can think of are Common Destiny (http://www.youtube.com/watch?v=UtXKBTr5NDk) and Camelot Links (http://www.youtube.com/watch?v=olEf8OLJ0ZI). Then there's also the Tales of Series Piano Arrange CD, which is purely piano without drums though (e.g. mislabled "Surprise Attack" (http://www.youtube.com/watch?v=emayn2Jk9Qc) and Burning Tower (http://www.youtube.com/watch?v=5pMpO6t4PAk)).

hum the tune and use this website:

http://www.watzatsong.com/EN/

they have a section for vgm.

Hm, how about Nascent Pulse (http://www.youtube.com/watch?v=zmtYT6Z6sec)? Not piano/drums only and different harmonics but still rather piano/drums focussed for its prog band style with a similar rhythm.

Could we please get some feedback on this, bark? It's been almost 3 weeks and you haven't said anything about whether you have figured it out or we need to keep searching.