That's a
huge understatement.
The tiny number of cases where someone was infected twice are outliers, and when you actually look into these, the most likely result is that the second infection is milder than the first, which is not surprising.
How severe were your symptoms? Milder cases do not generally see a strong antibody response. Also antibody levels may not be strong enough to be detectable after several months.
Of those I know who tested positive for Sars-Cov-2 most did not develop Covid-19 symptoms, and those that did were mild cases. This was a wide range of people including work colleagues, school students, forum members, etc.
However I do know several people who were seriously ill who tested negative, and had other viruses (one of whom was hospitalised with a rhinovirus).
www.sciencemag.org