The phrase "was proxy for" can have several synonyms depending on the context. In general, it means acting as a substitute or representative for something or someone else. Similar expressions could include "stood in for," "acted as a surrogate for", or "took the place of." More specific synonyms may depend on the industry or field of work, such as "represented" in legal or political contexts or "substituted" in sports or performance settings. Overall, using synonyms can help add clarity and variety to writing while conveying the same message in different words.