i assisted in your "ahem" spelling error as that wasnt the best choice of words
as for why it happens its so your game can work better, if the game kept all its generated stuff going you wouldnt have enough computer to run it and it would crash so to prevent that the game limits how long things are there for and tries to avoid having things vanish on you but its blind luck if and when that happens to you.
it definately is a PITA espesially if your torpedo is halfway there when they vanish but its something we trade off for having the type of AI this game has.