Have you considered filing a FOIA for raids on your apartment & the painting?
I didn't. I've never actually had to file a FOIA request before - is this something that would be available through one?
I would file one on yourself with all relevant agencies. It's a painless process (I emailed mine to the FBI), albeit a slow one.
What did you get back? Anything redacted?
Regarding the last part, have you asked if your landlord (or someone on their behalf) entered your apartment? For a newly rented out apartment, they may have had some kind of work to do or something to check over, and since you were away, may have just let themselves in.