I’d call his bluff. Whose radar does he claim tracked her?
In 1937, the best range for British radar was 60 miles. The Germans were still in the 3 mile range. A year later, the US could detect planes at 100 miles, but didn’t have operational ship mounted radar until 1939. The Japanese, although technically advanced, were far behind the west in deployment of radar.
I think the Itasca used radio triangulation