Missing foreign key entry in dev.toxicology.molecule table

The following statement fails with the error below:

INSERT INTO "atom" ("id","molecule_id","element") VALUES ('TR005_1','TR005','c');

Details: pq: insert or update on table "atom" violates foreign key constraint "atom_molecule_id_fkey"

The molecule_id TR005 doesn't exist in the molecule table AFAICT.

I'm wondering if anyone's encountered this - what they did to resolve it and if we could work together on cleaning up the data if necessary.