It's discussed in more details in other threads. There are conditions under which BA will exceptionally maintain your status for one year as a gesture of good will even if you did not formally qualify. I don't think anyone knows the exact criteria though I believe that they include the number of years when you qualified and how near/far you are from requalification. There is a separate question of people missing for life circumstances that BA is aware of (serious illness, etc) which can also be taken into account.

Glad you were granted an additional year of your status and hope the circumstances will improve in 2020.