it’s also possible the Quest antibody test is simply unreliable; most of the C-19 tests currently in use were never independently validated by the FDA for accuracy, but instead were “approved” on an emergency-only basis ...
unless a test has been thoroughly validated on thousands of subjects, some of whom are are known to be positive, some known to be negative and some whom are unknown, and all of this is done under rigorous conditions, a tst might have a very large false positive or a very large false negative rate, both, or those rates might be unknown ...
If done recently at Quest ($119.) this was a blood draw test (not a finger stick test)...the recently FDA approved Roche blood draw antibody test is close to 100% accurate. (Am not sure what brand test Quest is currently using).
https://www.zdnet.com/article/i-got-quests-new-covid-19-antibody-test-and-it-was-strange/
https://education.questdiagnostics.com/faq/FAQ219
https://www.roche.com/media/releases/med-cor-2020-05-03.htm