Possible spot on placenta

So I went in for my US yesterday a d they said baby is doing fantastic. Heart rate at 165 and prefect size for 7.5 weeks. They did take a long time for this ultrasound and I did have a miscarriage at almost 9 weeks back in November. She mentioned they want me to come back in 2 weeks for another in depth ultrasound. They saw a spot on my placenta. They said they can't tell at the moment what it is but should be able to determine more in 2 weeks. They said it could honestly be nothing or possibly a blood clot. Has anyone ever had an experience with this before? Just would like some advice since I'm not getting into the Google world of worry.