I agree. If booked on 2 separate tickets (check the ticket numbers as explained by the previous poster) there is a good chance that the return ticket will not be cancelled.

If it was me I would call PL once I "missed" the outbound flight and explain that you will actually take the return flight and ask PL not to cancel it. If the PL agent maintains that your return flight will be cancelled, point out the 2 separate tickets issue and escalate to a supervisor if neccessary.