Can Teemo Strategist be removed (e.g., with Gust) between being revealed from Hidden and his defense trigger resolving, and what happens to his effect?

Ruling: Yes, Teemo Strategist can be removed with Gust after his defense trigger goes on the chain but before it resolves. When the trigger resolves with Teemo in hand, you still reveal the top 5 cards but deal 0 damage because "here" (the battlefield location) no longer exists, so no enemy unit can be chosen.

Sequence:

• Teemo is revealed from Hidden when attacked
• His defense trigger goes on the chain
• Opponent can respond with Gust, returning Teemo to hand
• Gust resolves first
• Teemo's trigger resolves: you must reveal top 5 cards, but deal 0 damage since there's no valid "here" location
• Revealed cards are immediately recycled

Nuances:

• You still get to reveal the top 5 cards even though Teemo is in hand, allowing you to potentially get cards like Nocturne
• Targets are chosen when the trigger goes on the chain, but "here" is re-evaluated for legality at resolution
• If "here" cannot be determined (Teemo is in hand), no enemy unit can be chosen and the damage portion fizzles