non-detected

Adjective

 * 1) Having failed to be detected; not detected

Usage notes
Although similar to undetected, non-detected suggests that, despite active efforts, something has failed to be detected (perhaps due to some thresholding effect; e.g., "The concentrations ranged from non-detected to 100 parts per billion.") In contrast, undetected suggests that something has not been detected due to confusion or lack of awareness or effort (e.g., "Low levels of carbon monoxide poisoning can be confused with other symptoms of illness and can go undetected."; "Although the condition is common, it can go undetected if symptoms are mild.")

Related terms
undetected