Ectopic with absolutely nothing wrong with tubes?

Malori
Hey all
I had an ectopic back in May 2016 and I had an HSG done.... completely normal with no scarring... std test all negative... pelvic exams perfect so no PID, no endometriosis.... absolutely nothing wrong expect PCOS. My regular gyno even told me the two usual reasons I get ectopics are PID and endometriosis but I have neither. Nobody can explain why this happened. Has this happened to anyone else? Absolutely nothing wrong but still had an ectopic?