There is a penalty of $10k ( and Criminal penalties) if you fail to file.

Never simply throw up your hands and quit, criminals need to be punished.

There was a great deal of confusion as to whether this was a civil or criminal matter.  

Code §8-101 to 8-107 (Bad Checks)PenaltiesFelony: If the property or services has a value of $500 or more, a fine not exceeding $1,000 or imprisonment not exceeding 15 years, or both;Misdemeanor If the property or services has a value of less than $500, a fine not exceeding $100 or imprisonment not exceeding 18 months, or bothCivil PenaltiesA merchant or check holder may claim civil penalties separate from any criminal penalties against the accused.

I've seen proposals that criminal record can't be used to disqualify an applicant (not sure if it ever passed), so anything is possible. 

Any agent that wants to back door deal with you in that fashion and doesn't have these "arrangements" disclosed, would be committing a criminal offense if they executed the arms length affidavit without admitting a business relationship to one of the parties to the transaction.Sounds like your radar is working well in that you smell a car salesman.

You may also want to look into having criminal charges taken out against the tenant.

If I were to rent to them that would mean straying from my original perimeters set for tenants (good credit, 3X income, good rental history, no criminal background). 

She is betting that you are the kind of LL who pockets the application fee and rents without really running a credit/criminal/eviction check.

That means you either had 1. a loose key floating around, 2. a corrupt criminal with agent access who copied it, or 3.