Smartphone-based context-awareness holds significant promise for wheelchair users -- from detecting everyday accessibility barriers to enabling ability-based adaptations. Such capabilities often build on passive context inference through mobile sensing, yet their accuracy hinges on how and where phones are carried and the resulting signal quality. While prior work documents phone-carrying behaviors in the general population, patterns specific to wheelchair users remain underexplored. Through a mixed-methods approach combining a survey of 91 and interviews with 15 wheelchair users, we systematically investigate their phone-carrying locations and influencing factors. Our findings reveal distinct patterns extending beyond pocket storage to diverse wheelchair-mounted accessories and around-body placements, shaped by the interplay of physical ability, wheelchair design, and everyday contexts, including social, activity, and device factors. Grounded in these findings, we articulate how carrying location can serve as a proxy for user context to enable novel context-aware experiences, and discuss design implications for developing inclusive and effective mobile context-aware applications.

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