Happened to me, except the iPad bounced on carpet. Their Friendly Support is excellent, and sent a replacement quickly. Replacement was bowed too, before or during shipping.

They then offered a technique to micro-fracture the outer bamboo, but I'm not persuaded this would help it hold the iPad tighter.

I think they should consider changing the layers to counteract the curvature -- it should want to curve in to hold tighter, not curve out to hold less.

While assembling, they'd also have the option to pre-form the bamboo to a bowed in shape, then glue the layers while bowed. The glue would keep the bow in place, and use the aluminum (not gonna bow) iPad hold it back straight. The case might look odd without an iPad in it, but would grip much better when carrying the iPad.