[omnifischer]

May be you can say that "Trello handed over the only account you had to the previous company".

While I understand, the pain - I sympathize: please note that no permissions management system (or identity and authentication is so perfect that every case can be handled perfectly). As others say, you should have verified spent a bit of time to cleanup - because at the end - you lose time/money/whatever.

In the worst case, any company or even govt can just say sorry or some credits.

Even if the company is to blame 99 % you need to take 1 % responsibility.