This is a really stupid question but I don't know the answer..

So I had a vaginal ultrasound last week which would be about 15 weeks after I had unprotected sex (or there was another time where p/v made contact for a second I know that can still count without a condom) which would've been 10 weeks ago. Would a vaginal ultrasound pick up a fetus by then?? (There was nothing in there from what I could see on the screen/from what the sonographer told me)