R. advena
Pamela Slate (Tue, 24 Jun 2014 17:10:30 PDT)

Leo Martin wrote:
"Non-bulb enthusiast friends who visited Chile have talked about amaryllids
growing on
the coast in sand a hundred meters or so inland from the sea. Their
description sounded
like R. advena. Is this likely?"

Looking at this page from Chileflora, seems like your answer could be yes.

http://chileflora.com/Florachilena/FloraEnglish/…

You will note the soil type and elevations.

P. Slate