I have had this experience a few times...actually it is pretty frustrating. One time it was the weather as it was nasty and in the scope I could see the ship floundering. In another instance it was friendly forces (in this case an air strike), I was approaching and popped my scope up to see that the merchant was burning...wtf!? he was just fine a minute ago, a couple minutes later I see splashes...hey its the luftwaffe! I also think mines and friendly surface ships also can take out your prey if they get the chance
