Mercury 90 Hp Outboard Shredded Impeller

My Mercury 90HP two stroke (2004 model) ate its water impeller this weekend. It left me stranded miles from the boat ramp. Not a comforting feeling, especially when I changed the 10 year old impeller out for a new (aftermarket) one six months ago. Yes, the previous owner never changed the impeller.

Anyway, I pulled the lower unit off and popped open the impeller housing to find an impeller with one of six fins/tines left intact. I found four of the other fins inside the water pump housing, but could not find the last one.

Should I be concerned about the last one? Could it have been sent "upstream" into the upper unit and get lodged somewhere? Given that impellers fail all the time, I would assume that Mercury would design something to catch foreign objects in the water lines. But I don't know.

Any help you can offer is greatly appreciated. Needless to say, an OEM replacement impeller is on its way to me.