So the lab wasn’t hidden. It was known by the all-knowing-massive-cannot-do-anything-right government.
‘Hidden’ is probably the wrong word to suggest.
They had a parking lot...employees (non-American)...a mail-box....electrical power (I assume monthly bills paid). I assume a telephone patch brought in the internet connectivity.
They could have just as well, run a meth lab, and not been noticed.
I think it’s a five-star script worthily of a Netflix series, similar to Breaking Bad. ‘Hu-Won And The Temple’ would be my title.