Forming antibodies (antibody driven adaptive immunity) seems like the most likely way patients are recovering. This would be typical of recovery from Coronavirus infection.

https://www.nature.com/articles/s41591-020-0819-2

I can’t find any research suggesting that patients (symptomatic of not) are recovering in some other way.

And in any case, recovery implies some form of immunity, either innate or adaptive. The virus doesn’t just give up after 14 days.