I have noticed that there are constant locations where there is money on the ground, random ammounts. No monsters there, I have not killed stuff.
What`s that about? Is it a sign / bug / feature / suuuuup!
You might have attacked a treasure goblin that was off screen and just not noticed.
Treasure goblins would leave a long trail of gold before they teleport out. The gold the OP is talking about is just a single pile here and there. I've seen those too myself, and yes, I did look for a goblin when I saw gold on the ground. Like I said though, goblins would leave a long trail of gold which would be relatively easy to recognize.
Happens to me too in act 3 - the crater. I zone in to a fresh map and there's money on the ground visible from the portal without moving. It's not from a goblin or anything like that, because like I said it's a fresh map and I haven't moved an inch yet. I think it's from the environmental things, like the flamethrowers. But that's weird because that would mean the maps are active before you zone into them. Not sure exactly where they come from.