Letrozole 1st round 4th ultrasound showed burst follical

Shannie • ♡Shannie•29•Married•TTC#1 for 2 years•PCOS•Chronic illness•Pitbull momm. ♡
I'm taking 2.5 letrozole on my first round I have pcos so I'm not supose to ovulate on my own .... but on cycle day 2o I had an ultrasound and it showed my dominant follical burst so they think I ovulated? Thus meaning i dident get my trigger shot ... has anyone experienced this??