There's no hard and fast rules for when anyone will feel baby, no matter how many pregnancies. It can depend on how and where baby is lay, your body shape, placenta location, etc. The lady saying your placenta is in the perfect spot may not mean it's anterior, she may simply mean it's up away from the cervix and not at risk for Placenta Previa.
I'm on my fourth baby and have an anterior placenta for at least the third time. I first felt ANY movement at around 16 weeks and it was only one quick movement when I was lay in a particular spot. It took another few weeks after that to feel anything regularly. Even now at times I have noticed that I can hear baby swishing around on the Doppler but not feel it, so she must have her legs/arms pointing the other way.
15 weeks is way too early to be worrying, it's not unusual to not be noticing movement yet xxxxxxx