Should I be worried

Amaya

So my partner said he could feel my iud one night and that’s not supposed to happen soo I went to the doctor and they couldn’t find the strings so I was sent to get an ultrasound they did a transvaginal and regular and called me saying that the iud wasn’t noted but is “probably in the correct place” but my question is how can you determine something is possibly in the right place but you didn’t see it? Should I be worried ?