The opposite of being on hand can be described in different ways. One antonym could be "absent," meaning someone or something is not present or available. Another antonym could be "unavailable," which suggests that a person or item is not within reach or is isolated. "Inaccessible" is another antonym that means something or someone is difficult or impossible to reach or approach. The term "inexpedient" could also be considered an antonym, describing situations when something is not convenient or suitable for the circumstances. Finally, "unprepared" is another antonym that suggests a lack of readiness or planning for particular needs or unforeseen events.