Raids: The Unwritten Rule?

[Kikoten]

Hello.

I've recently had an experience in a World of Darkness raid where I became the center of accusation for someone in my alliance. Allow me to explain:

I queued as a WHM. In an instant, the queue popped, and it turned out that I joined a party in progress.

I used the wormhole device to teleport my way to the group's current location: the second(?) or third(?) boss. I was, of course, gated out. As I watched on, I performed a merry step-dance as my new party swiftly and effectively took down the boss.

The gate dropped.

I joined up with the party as we ran on to the next encounter. There, we took down the boss, and here's where it began. A piece of loot came up.

I moused over the loot, saw a bunch of green numbers, saw the word "Healing," and noticed it was an upgrade. Because I'm trying to gear up beyond Daystar in preparation for Heavensward, I instinctively clicked "Need" without thinking.

I won the piece.

The other healer in the group told me that I suck, gave me an angry emoticon, and left.

Okay, he must've been farming for the loot. I wanted to apologize, but he just left too quickly.

I was then told that I "stole his loot." And that I "better be on the ball and not fuck this up" during the upcoming boss, being I supposedly stole the other healer's loot and drove him away.

So my question is this: Do raids have an unwritten rule, where if you join a group in progress, you can't roll on upgrades? Is it considered "stealing" to outroll someone?