Same thing happened to me with some linen cloth a few years back. Portland customer too, funny enough. I started taping a little arrow on the back of every roll showing the grain direction before it goes into storage, saves me from second guessing myself when I'm in a rush. The real fix was testing it the same way the customer must have, wetting a scrap and seeing which way it curls. Now I do that with every new batch before I cut anything, takes two minutes and costs me almost nothing. Havent had a single complaint since, and it forces me to slow down and actually handle the material before I trust it.