This can now be marked as "Fixed" again.
The reason it didn't work is that it tries to teleport you to "Muelle_shore_01", which might have existed at one time (there are "Muelle_shore_02" and "Muelle_shore_03" defined in "PROGRAM\Locations\init\IslaMuelle.c") but doesn't any more. Looking at "quests_side.c", specifically case "to_muelle_for_letter" (which, by the way, uses "SetFleetInTown" to place your fleet after you've teleported to the beach to meet the redshirts - er, redrobes) it needs to be "Muelle_shore". Setting "pchar.location.from_sea" to "Muelle_shore" in case "with_teacher_to_muelle_3" fixed the problem - after the meetings with the Teacher, I hiked over to Oyster Beach again and this time my ship was there.
The reason it didn't work is that it tries to teleport you to "Muelle_shore_01", which might have existed at one time (there are "Muelle_shore_02" and "Muelle_shore_03" defined in "PROGRAM\Locations\init\IslaMuelle.c") but doesn't any more. Looking at "quests_side.c", specifically case "to_muelle_for_letter" (which, by the way, uses "SetFleetInTown" to place your fleet after you've teleported to the beach to meet the redshirts - er, redrobes) it needs to be "Muelle_shore". Setting "pchar.location.from_sea" to "Muelle_shore" in case "with_teacher_to_muelle_3" fixed the problem - after the meetings with the Teacher, I hiked over to Oyster Beach again and this time my ship was there.