Say that the route is unknown and provide any installation documents. Do not dismantle walls or open pipework to trace wastewater yourself.
What the observation means
The route can matter to a repeated fault or replacement assessment. A pipe disappearing into a wall does not prove where it connects.
A useful next step
Describe visible sections and known alterations from a safe position. Let the appropriate professional investigate. Do not connect the discharge to another convenient drain or assume an outdoor pipe is suitable without proper installation assessment.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.