That might have been what happened to the sentinel that landed in Iran.
A sentinel is present 24 hours a day, seven days a week, 365 days a year, including holidays.
They may be taking some action in the future, given the weaknesses that appear to have been exposed in the sentinel.
1570s, from Middle French sentinelle (16c.), from Italian sentinella "a sentinel." OED says "No convincing etymology of the It. word has been proposed," but perhaps (via a notion of "perceive, watch"), from sentire "to hear," from Latin sentire "feel, perceive by the senses" (see sense (n.)).