Chances of not catching retained embryo

My first FET, our embryologist found that our little embryo was retained in the catheter. They did a second transfer, which resulted in our first baby, and I am forever grateful. We really feel like our baby came close to being thrown out with the garbage that day.

We are now trying for a second baby, and I am feeling really nervous that the embryologist won't look hard or long enough and miss the retained embryo. As we are trying for our second, our doctor totally dismissed our concerns and insisted that there's no chance the embryologist can miss a retained embryo. As much as I want to believe that, people make mistakes, and how could they possibly know whether they missed something?

So, I am wondering if any embryologists or others in the community can share insights on the possibility of the embryologist missing a retained embryo in the catheter. Thank you.