A Big Walk missing puzzle is easiest to find by separating main-route progression from the later completion cleanup. The official FAQ confirms that the adventure has an ending, while player completion reports show that finishing the main route and completely finishing the game are different goals.
Check the map before repeating the island
The map room opens through Red Tower progression and contains a three-dimensional terrain model plus a portable map and compass. The terrain model develops as the group explores, so revisit it after checking an unfamiliar area rather than assuming every blank or unfinished point represents the same kind of task.
Record each unresolved structure by its color, nearest tower or transport stop, and the object that appears to be missing. Because the game does not present a conventional named quest log for each puzzle, location-based notes are more reliable than trying to remember a puzzle by order.
Separate tower progress from extra puzzles
The opening beach sequence is tied to reaching the crosswalk, but after that the world becomes more open. A published set of tower walkthroughs notes that nearby puzzles are practical recommendations rather than permanently assigned tower quests, so a remaining tower slot does not necessarily identify one specific puzzle.
Check whether your group needs another ordinary reward for progression, a purple reward from the late-game area, or an unresolved puzzle that contributes to complete completion. These are different search jobs and should not be mixed into one unchecked list.
Build a useful missing-puzzle record
For every unfinished spot, write down the map area, structure color, visible symbols, sound, number, required item, and whether a reward container is present. Add one screenshot if the clue is visual. This creates a searchable description that another player can recognize without relying on an unofficial name.
If a structure appears solved but progress did not update, reload the host's saved world before repeating unrelated puzzles. The official FAQ states that the game autosaves and that the host is the keeper of progress, so confirmation must happen in the same host world rather than a different player's session.