Hmmm. So there should be a runway check if there's debris on the runway ? That doesn't make sense.
The original poster has simply poorly worded his sentence (bad syntax)
If there was a check of the runway before takeoff of the Concorde Titanium piece was discovered
But there was no such inspection .. and there were three options
1 No one piece of Titanium (nothing can happens)
2 Piece of Titanium and tire does not touch (luck)
3 Piece of Titanium and tire passes on (bad luck)
Luck is not a safety factor