I realize this thread is quite old, but this is for anyone else that ends up here.
The current version of Immunet at the time of this writing stores it's history in C:\Program Files\Immunet\history.db
This file is a SQLite3 database file which can be opened with any SQLite3 client with no credentials. In my case this was PowerShell using PSSQLite.
This database file contains one table with the following DDL:
CREATE TABLE history (
If you're only interested in detected files like I was, this query should provide what you are looking for:
select * from history where detection <> '';
Other database files which may be potentially useful to you are: