I do recall reading about a Union soldier who gave the Masonic sign of distress to a Texas Confederate during the Battle of Chickamauga. As the story goes, the Federal, who was wounded requested water, and the Confederate gave him his canteen and moved on. This story was told by the Texan postwar, and as the story goes, the soldier didn't think of his canteen until some years after the war when he saw an ad in a newspaper from the Union soldier requesting a meeting with the Confederate soldier who gave him his canteen. Both veterans met, with the Union veteran being on his deathbed where he (Union Vet) returned the canteen to the Texan, and also a monetary reward as well.

If I am not mistaken, I believe that I read of this account in an issue of the Confederate Veteran Magazine.