Legal analysis: whether the gym is responsible for losing things depends on the situation. Operators, managers or organizers of mass activities in public places shall bear tort liability if they fail to fulfill their security obligations and cause damage to others.

Legal basis: Article 1 198 of the Civil Code of People's Republic of China (PRC). Operators, managers or organizers of mass activities in hotels, shopping malls, banks, stations, airports, stadiums, entertainment places and other business places shall bear tort liability if they fail to fulfill their security obligations and cause damage to others. If the behavior of a third party causes damage to others, the third party shall bear the tort liability; Operators, managers or organizers who fail to fulfill their security obligations shall bear corresponding supplementary responsibilities. Operators, managers or organizers may claim compensation from a third party after assuming supplementary responsibilities.