Eddie,

My condolences. I guess the rotor area is not enogh to autorotate

With a wing loading of 57.6 oz/ft*2 and cruising at around 40mph, by your estimate, you didn't have much of a chance of recovering from that low altitude. Here is a graph that I got out of "Basics of R/C Model Design" by Andy Lennon. The original graph did not include wing loadings as high as yours, so I projected the lines further out to the right (blue lines). Your wing loading is the red line. I don't suppose you know the lift coefficient of the Isobar wing's airfoil? If you do not know the lift coefficient of your airfoil Andy Lennon mentions that most airfoils have lift coefficieents of around 1.0. Assuming that your lift coefficient is 1.0 your stall speed projects out to 37 mph.