Question: Who did Hayek work for after being hired by the author of Human Action?

Knowledge 1: Human Action
Human Action: A Treatise on Economics is a work by the Austrian economist and philosopher Ludwig von Mises. Widely considered Mises' "magnum opus", it presents the case for laissez-faire capitalism based on praxeology, or rational investigation of human decision-making. It rejects positivism within economics. It defends an "a priori" epistemology and underpins praxeology with a foundation of methodological individualism and speculative laws of apodictic certainty. Mises argues that the free-market economy not only outdistances any government-planned system, but ultimately serves as the foundation of civilization itself. [SEP] Knowledge 2: Friedrich Hayek
During Hayek's years at the University of Vienna, Carl Menger's work on the explanatory strategy of social science and Friedrich von Wieser's commanding presence in the classroom left a lasting influence on him. Upon the completion of his examinations, Hayek was hired by Ludwig von Mises on the recommendation of Wieser as a specialist for the Austrian government working on the legal and economic details of the Treaty of Saint Germain. Between 1923 and 1924 Hayek worked as a research assistant to Prof. Jeremiah Jenks of New York University, compiling macroeconomic data on the American economy and the operations of the US Federal Reserve.
Knowledge 1: Human Action
Human Action: A Treatise on Economics is a work by the Austrian economist and philosopher Ludwig von Mises. Widely considered Mises' "magnum opus", it presents the case for laissez-faire capitalism based on praxeology, or rational investigation of human decision-making. It rejects positivism within economics. It defends an "a priori" epistemology and underpins praxeology with a foundation of methodological individualism and speculative laws of apodictic certainty. Mises argues that the free-market economy not only outdistances any government-planned system, but ultimately serves as the foundation of civilization itself. [SEP] Knowledge 2: Friedrich Hayek
On his mother's side, Hayek was second cousin to the philosopher Ludwig Wittgenstein. His mother often played with Wittgenstein's sisters, and had known Ludwig well. As a result of their family relationship, Hayek became one of the first to read Wittgenstein's Tractatus Logico-Philosophicus when the book was published in its original German edition in 1921. Although Hayek met Wittgenstein on only a few occasions, Hayek said that Wittgenstein's philosophy and methods of analysis had a profound influence on his own life and thought. In his later years, Hayek recalled a discussion of philosophy with Wittgenstein, when both were officers during World War I. After Wittgenstein's death, Hayek had intended to write a biography of Wittgenstein and worked on collecting family materials; and he later assisted biographers of Wittgenstein.
Knowledge 1: Human Action
Human Action: A Treatise on Economics is a work by the Austrian economist and philosopher Ludwig von Mises. Widely considered Mises' "magnum opus", it presents the case for laissez-faire capitalism based on praxeology, or rational investigation of human decision-making. It rejects positivism within economics. It defends an "a priori" epistemology and underpins praxeology with a foundation of methodological individualism and speculative laws of apodictic certainty. Mises argues that the free-market economy not only outdistances any government-planned system, but ultimately serves as the foundation of civilization itself. [SEP] Knowledge 2: Friedrich Hayek
Hayek’s concept of the market as a spontaneous order has been recently applied to ecosystems to defend a broadly non-interventionist policy. Like the market, ecosystems contain complex networks of information, involve an ongoing dynamic process, contain orders within orders, and the entire system operates without being directed by a conscious mind. On this analysis, species takes the place of price as a visible element of the system formed by a complex set of largely unknowable elements. Human ignorance about the countless interactions between the organisms of an ecosystem limits our ability to manipulate nature. Since humans rely on the ecosystem to sustain themselves, we have a prima facie obligation to not disrupt such systems. This analysis of ecosystems as spontaneous orders does not rely on markets qualifying as spontaneous orders. As such, one need not endorse Hayek’s analysis of markets to endorse ecosystems as spontaneous orders.

Answer: the Austrian government