Another idea:

在设定s > Module > Line Items

you can donwload to excel and search in the "Formula" column if you are referencing that list.

Also, you said "I have gone through every module that has this list in its "applied to" and removed any references to its current parent list". It's possible to have a line item that has this list in its "applies to" even if the module doesn't (subsidiary view). This excel export can also help yiu with that.

Hopefully you can find the reference quickly. Keep us posted!