The aim of this article is to present Jan Patočka's reading of Heidegger concerning the issue of technology as a key for understanding Patočka's phenomenology of appearing in relation to Heidegger's phenomenology of the unapparent. Assuming the essence of technology, defined by Heidegger as Gestell, to be considered as an ontology of sacrifice and salvation, Patočka shows that appearing as such implies a sacrifice. This sacrifice can be called a "phenomenological sacrifice." The ensuing reflection is divided into three parts: (1) a summary of Patočka's understanding of the difference between Husserl and Heidegger as regards the phenomenological question of technology; (2) a general discussion on the question of technology as a question of Being qua appearing and the unapparent; (3) an outline of what I call "phenomenological sacrifice" as the sacrifice of appearing, through a discussion of both Heidegger's and Patočka's views on the essence of sacrifice.