The rate is not the cost
When a carrier blanks a sailing, the container you booked simply does not go. You are rolled to the next service, and on a weekly string that is seven days. The rate you agreed still stands, so on paper nothing has happened.
What has happened is that the origin storage clock started, the receiving window at the far end is now wrong, and any onward booking you made against the original arrival has to be moved. On a retail lane, that is the part that costs.
Why they blank
Carriers cancel sailings to hold rates when demand falls, and to reset a schedule when a string has fallen behind. Both are commercial decisions taken centrally, usually two to three weeks out, and both are published.
That publication is the opening. A blanked sailing is visible before your container is affected by it, which means the conversation about the new date can happen before the cutoff rather than after it.
How we handle it
We watch the schedule for the strings we book on rather than waiting for the carrier to tell us a specific booking has moved. When a service is pulled, the customers with cargo on it get a call the same day, with the next two confirmed options and the price difference between them.
Sometimes the answer is to wait a week. Sometimes it is to take a transhipment service that arrives four days later than the original but three days earlier than the roll. Occasionally it is to air freight the part of the shipment that has a deadline and let the rest sail. You can only choose between those if somebody tells you early.