(May 3, 2016, 9:31 AM EDT) -- ST. LOUIS — The Eighth Circuit U.S. Court of Appeals on April 29 affirmed a district court’s ruling that an insured failed to prove its affirmative defense of estoppel against the insurer, noting that it is clear that the insured knew or should have known that the insurer was reserving its rights (National Surety Corp. v. Dustex Corp. and Miron Construction Co. Inc., No. 15-2096, 8th Cir.; 2016 U.S. App. LEXIS 7757)....