provisional played when ball "might" be lost OR in a hazard
this gets confusing but I think I know what's right.
You hit ball, there is a hazard, you aren't sure if it's in, or maybe you didn't know it was staked, you declare and hit provisional.
Get up there and can't find ball anywhere. I see two results
1) if you can't be virtually certain ball is in hazard, declare it lost and play provisonal
2) if you can deem the ball lost in hazard, take appropriate drop and play on
the question is deeming the ball lost or in the hazard. Not finding the ball does not mean its in the hazard, although in the case where it's wide open and mowed every where else it might be what tips the scales to be "virtually certain". If it flew into what you later find out to be a marked hazard area, I suppose it could have always bounced out somehow, but if there's no ball anywhere I'd call this in the hazard. We can only do our best right?