Had to pee, decided WTH and check to see if I could find the heartbeat again.
Checked in the general area of where I had found it before and there it was. It took a minute and it was faint, but it sounded like a little train just chugging along. So happy I can have some reassurance.
Will try to get a video of it maybe next week or 2. We'll see what happens and how often I can find it, how loud it is.