Originally Posted by
JAXBA
The invol reroute through AMM for CAI-DOH won't hurt/count against the 16 coupons, especially as the only the first two coupons were exchanged, leaving the remainder of the original ticket as a visual clue as to what happened and why. There may be some pushback later on if what happened and why isn't immediately obvious, but it's easily explained: it was involuntary, and should be considered as having flown CAI-DOH on a single coupon. 
Out of interest: What do they put in the fare calculation box of the second ticket? Just leave it blank?