My landlord sub-let to me. I've moved out. Owners coming after her [ex pat in Germany]

Hi guys,

I took a sub let at the beginning of the year from a girl. I paid her a bond, but we did not sign any lease agreement.

I've now moved out, got my bond back and she and I are on good terms. But she has called me in tears saying the apartment owner is claiming she was not allowed to sub let (when in the past they said she could) and now have lawyers writing to her claiming that I was living there for many years, blah blah blah.

This is not true, I lived there a few months. We suspect the owners just want to get rid of her so they can sell for big cash, but anyway, do I have anything to be concerned about in terms of my liability?

tl;dr I was sub-let an apartment. No paperwork signed. Paid a bond and it's been returned. Now the owner is pursuing the girl who sub-let to me to say she didn't have the right to do this. Am I legally liable?