He didn't retrieve Tesla's work himself.

"P. E. Foxworth, assistant director of the New York FBI office, was called in to investigate. According to Foxworth, the government was "vitally interested" in preserving Tesla's papers. Two days after Tesla's death, representatives of the Office of Alien Property went to his room at the New Yorker Hotel and seized all his possessions.

Dr. John G. Trump, an electrical engineer with the National Defense Research Committee of the Office of Scientific Research and Development, was called in to analyze the Tesla papers in OAP custody. Following a three-day investigation, Dr. Trump concluded:

His [Tesla's] thoughts and efforts during at least the past 15 years were primarily of a speculative, philosophical, and somewhat promotional character often concerned with the production and wireless transmission of power; but did not include new, sound, workable principles or methods for realizing such results."

https://www.pbs.org/tesla/...

Yes, but John Trump's findings that the work "did not include new, sound, workable principles....." was a smoke screen. What he found was profound and he knew the gov would use it for nefarious purposes so it was an attempt to discourage them from further investigation.