Police database
When Sullivan was running the names/SS# from the citizens envelope through the police database, we initially see that a search for Billy's name did not reveal anything about him. However later in the film, after the shootout scene Billy is debriefed and waiting to be paid. When Sullivan runs his name again, we see that Billy's name shows up in the database but is password protected (with his own name, comically).
Was this a mishap on their part or was this explained?
"When there's no way out, you find a deeper way in."