> This requires a specific set of actions by a crewman on the bow.

That's not true. While well maintained equipment would require a specific action, it is not uncommon for accidental anchor drops to happen, typically due to poorly or improperly maintained equipment. It's also common that ship is unaware that it has dropped the anchor (depending on the depth of the water, the anchor may not even have much effect, but even if it does it's not always identified).

For example, here's a report from a US based ship accidentally dragging anchor for a couple days: https://www.ntsb.gov/investigations/AccidentReports/Reports/...