I doubt this will have much bearing after the 5.2 patch hits (next week?) since forfeited matches won't de-spawn wild pets, but for those of you who have always been curious...
If a pet is captured during the same round that it dies, you will still get credit for the capture. For example, you weaken a wild pet with Flamethrower then attempt to trap it. If your trap animation closes around the pet AND the ticking damage from Flamethrower kills it on the same turn, you will still have that pet added to your collection assuming you can eliminate the other wild pets on the team. Mystery solved.
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