Worried :/

Samantha ⚓️
I've been using an app on my phone for weeks now that can hear the baby's heartbeat. Been able to hear a strong one for weeks now. When I tried this morning, I couldn't find anything at all. I'm really worried that there isn't going to be a heartbeat at my appt on Friday :/ has this happened to anyone? Please give me reassurance. I'm terrified.