Hi Legal advice,

I'm using a throwaway because this is all just too crazy and honestly I'm embarrassed. I made some mistakes, and now I need to make sure I'm protecting myself as well as possible.

So backstory:

My girlfriend of a year and I broke up amicably. She had been living with me, and being the type to bend over backwards I offered to help her pay her rent until her student loans came through (next month). The only place she could find wanted 4 months rent up front (claiming she was a student, with no real credit history). It made sense, at least when I thought she would be paying a leasing company.

Here's what happened: I found out her new landlord/roommate (L/R) wanted the check made out not to her, or the apartment owners, but to a 3rd party business she owned. I was a little creeped out, but, she "needed" this place and she said she trusted the woman (She had met her 3 times prior to this meeting, where as it was my first meeting). We provided her new L/R with a check for 1850 (rent for 4 months + deposit) made out to this 3rd party company of hers. In exchange we received a receipt stating she would not cash the check until lease signing and move in the next week (I asked myself how unusual this was, and I know I should have put my foot down here, but I was feeling guilty and wasn't thinking clearly yet).

So lease signing and move in time came. This new L/R did not have the lease ready to be signed yet, but said she could move in anyway. Then all hell broke loose. She used a padlock to lock my ex in with her the first night "to prevent someone from breaking in off the street" but did not provide her a key to be able to get in or out of the apartment. She then said in the morning that she had lost the rent check I provided (which has not as of yet been cashed), and that she wanted me to issue her money by transfer immediately because she needed to leave on Monday and it needed to be in her account by then or my ex could not stay.

Feeling creeped out by being locked in all night and even worse about needing to have me cancel a check and potentially issue a new one or set up a transfer my ex decided to just leave this apartment.

I came over to pick her up and got a 911 text from her, turns out her new L/R would not open the door. She was keeping the padlock on the chain holding the door shut and demanding she be paid a minimum of $300 cash for her "time" before she could leave. Well I call the cops, they force her to let my ex out, the L/R throws most (not quite all) of my ex's belongings out the window. We talk with the cops a bit more and they send us on our way cautioning "that its probably not worth the time and risk to enter the house for the groceries and cat litter she still has".

So where that leaves me is with a check that I do not want cashed, still possibly in the possession of a very clearly mentally unstable person. I have cancelled that check with my bank, I have additionally put out a global cancellation on any checks for 1850 from my account and any checks to the name of that business.

What I'm asking:

Is there anything else I can/should do to protect my accounts from this mentally unstable woman? I know I fucked up, but I'd love it if I don't lose any more than the 5 hours rescuing my ex and the cuts on my hands from sorting through the bags she threw out the window containing glass jars.

And also she claims to have gone to law school, and made it clear (as she screamed out the window while throwing my ex's belongings) that she will use the name and address available on the copy of my check that she has to "sue me into the ground". I'm wondering if there's anything I should do to be extra prepared if she does attempt to sue me and if you over here in legal advice have any ideas of what on earth she could try to file for seeing as how she was the one who held someone against their will.

TLDR: My ex moved in with a crazy woman, spent 1 night without signing the lease, all hell broke loose, she's out and not going back. How do we make sure she doesn't try to cash the check we gave her (which she claimed to have lost)? How do I protect myself?

Thank you so much in advance for any advice.