The phrase "is lost" can be substituted with various alternative words and phrases that adequately capture the intended meaning. These include "has disappeared", "is missing", "is gone", "can't be found", "has vanished", "is misplaced", and "is absent". Each of these options adds context and a nuanced meaning to the phrase, depending on the situation or condition described. For instance, "is missing" suggests an unexpected disappearance, while "is misplaced" connotes a milder situation where an object is not lost forever. Ultimately, these synonyms offer more descriptive possibilities in communication, adding depth to a sentence and refining its intended message.