Johonso. It is of course not a line holders responsibility to check his schedule like a reserve pilot. You notify after the awarded trips are on your LOT the month prior.

If they pull your trip, it is their obligation to call you.

Scambo;
If you report for the original trip, you are then under the control of the LCA. He can release you at the gate as I have had done many times. They may or may not have recovery at that time.