Interestingly enough the census (which I believe is the source the WH used) https://www.census.gov/foreign-trade/balance/country.xlsx does show trade with Heard & McDonald. Also reflected on the webpage: https://www.census.gov/foreign-trade/balance/index.html#H

Now what the underlying items are that were traded? Not sure. Guessing you can dig it up in AES https://www.census.gov/foreign-trade/aes/index.html but have not been able to figure that out. Let me know if you do.