It's always possible it was something else, but lack of (testable) antibodies does not rule out COVID-19 infection, as they are not always developed and/or expr

It's always possible it was something else, but lack of (testable) antibodies does not rule out COVID-19 infection, as they are not always developed and/or expressed after some time. Seems like that may even be common. Since T-cell immunity is rather hard to test, you may never know.