While I agree with Macman's comments that an IW isn't acceptable - any official that tells you he hasn't had an inadvertent whistle is either a brand new official, or he's lying. 
While my personal record is of no importance, for the record, ay no time did I say I'd never had an IW. In fact, 39 years ago, I had one, while working intra-mural football my second year in college. Guess what - I was carrying my whistle in mouth, at the time. Started carrying it in hand after that, and I haven't had one since. Solely because of carrying it in hand? No. A combination of carrying it hand AND being conscientious about making sure I see the ball in possession with the BC "down" or progress stopped. If in question, no whistle until there is no question.
Was my IW fatal? Thankfully, no. Not for intra-mural football. But, one was too many. As Grant noted, folks at more advanced levels have been released after having an IW. Was that the sole reason for their release? Who knows? But, the IW was their kiss of death. Has everybody that ever had an IW at advanced levels been released? No. I've been involved in two games in which another guy on the crew had an IW. Neither were released. Their coordinator was (is) one that was (is) more more understanding and forgiving than, perhaps, any other in the business - ever. But I know of coordinators that would fire their mother if she had an IW.
As Jason says, "Back on track."
Remember: the only whistle that makes the ball a live-ball dead is an inadvertent whistle. In all other cases, the ball is already dead, and the whistle is just an
aid to let the players know that the play is over. If, occasionally, the whistle is delayed because no official can see the ball with possession/down/progress stopped, that's OK. The play is still over. On very infrequent occasions, you might not even have a whistle after a play. Nobody sees ball/possession/down, and the next thing a player is handing the ball to the U, or, by the time the U gets to the downed BC, it is SO late no one wants to look silly by sounding a whistle at that time. Those things happens - very occasionally. Unfortunately, some guys think it is 'cool' to frequently not have whistles. That is a dangerous practice. Blockers leading a BC can not be expected to keep looking back to know if he is down, or still advancing. They have a right to expect to hear a whistle as often as possible to alert them that the play is over, and to discontinue action. That's why we have whistles to begin with. When we don't have a whistle at the end of a play, there is greatly increased risk of a player drawing a late-hit foul for blocking after the dead-ball. Personally, I've had to make that call, as distasteful as it was. Those responsible for progress and/or seeing the BC down, COULD have sounded a whistle, but simply chose not to. Well after the BC was down, a blocker knocked the crap out of a defender beyond the pile. I had no choice. If we'd had a timely whistle, that foul would not have happened.
So, have a whistle, but avoid the IW. Easy? No. That's why we get paid the big bucks.
