It’s very common to drop /h/ in “he” after a consonant, so “when he” sounds like [wɛni].
Note also how the /t/ in “got” is dropped; the voice stops and as the lips close for ‘b’ in “back,” we hear an unreleased /p/.
when he got back to his desk
[wɛnigɔp˺bǽk˺tɪzdɛ́sk]
[wɛnigɔp˺bǽk˺tɪzdɛ́sk]