[...] he pulled out his phone and cancelled his flight to Hawaii.
The only word I can think of is languishly. But I think it's not used very often in that way.
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The adjective form is lackadaisical.
lackadaisical [lak-uh-dey-zi-kuh l] adjective 1. without interest, vigor, or determination; listless; lethargic: a lackadaisical attempt. 2. lazy; indolent: a lackadaisical fellow.
One more: indolently.
lethargic: (adj.) feeling a lack of energy or a lack of interest in doing things