For bookings I think your best bet is to contact Iberia direct, particularly since it is not a daily flight.

All I did was to check availability and price for SJO-PTY using the first online website I came up with (rumbo.es, in this case) and could see that the IB flight was valid and priced. I didn't check the return flight, but if it exists then it stands to reason that it should also be valid.
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