i tested positive for cocaine and never used. is there a possibility it got in my system during sex?

this is a crazy ass situation. i’ve been hooking up with this guy for 2 mos. i suspected drug use bc he’d constantly blowing his nose. it’s always runny or stuffy. this past thanksgiving, we met up and my suspicion were confirmed. he does coke. and he did a SHIT ton of it in front of me. back to back. it was non stop. that was the first time i’ve seen him do it. told him to stop or he’ll ’speed bump’. i was at his place for a week and we had sex a lot. he wanted to do a line of it off my ass and i told him no. (yeah shit don’t make sense to continue to hook up with somebody that’s a heavy user.) the day of me leaving, i finally receive the email to do my drug test for a job. i’m prescribed controlled substance, i wasn’t worried. fast forward a few days later, an MRO called and said i tested positive for coke…. pissed off is not enough to describe my emotion because i’ve never touched, ingested that in my life. i asked him did he put any of stuff on his dick and he told me no. orally, my mouth never went numb since coke can have that novocaine feeling. he never let me touched the bag and it was in his possession. the cocaine level was 269nl/mg in my system and the cut off level was 300nl/mg. none of this makes sense to me and i’m 100% sure i’m not getting the job. i just don’t get how i tested positive for something i never did…….