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The water bottle stopped being yours once you left the venue. The event staff took ownership of it, as well as the other thousands of water bottles left after the event, and disposed of anything that could cause problems. That's is a custodian's job description, it's not just about cleanliness, it's also about safety. All liability falls on the venue for possible safety violations, so they did their job, and made things safe for everyone. Including you.

Peace comes with acceptance and understanding. Keep up the good work, stability is a virtue!