I play Scuttle Crab on the battlefield, then my opponent reacts with Gust. Did Scuttle Crab still draw a card?

Yes, you still draw a card.

According to the rules and game mechanics for "When you play me" triggered abilities:

1. Triggering: When you play Scuttle Crab, its "When you play me, draw 1" ability triggers as soon as the unit enters the battlefield.
2. The Chain: Triggered abilities are placed on the chain. Even though your opponent responds with Gust to return the Scuttle Crab to your hand, the triggered ability is already on the chain.
3. Resolution: The chain resolves in Last-In, First-Out (LIFO) order. Your opponent's Gust resolves first, returning the Scuttle Crab to your hand. Then, your "draw 1" ability resolves, and you draw your card.

This interaction is consistent with established rules for "When you play me" effects, such as those seen in RiftJudge FAQ #8895 regarding the Lecturing Yordle. Once a triggered ability is on the chain, it will resolve regardless of whether the source unit is removed from the battlefield before the ability resolves.