yeah that's a call of right vs. wrong. I say if the company will pay for you to ship it back and send the jib quickly so you dont lose any extra money or time then you should give the main back to them. If they had tried to be real jerks about it and make you pay to ship things both ways or something then for me it would depend on the size of the company. If I'm buying from some huge seller that makes millions of dollars then they wont miss the sail at all. If it's a smaller one though, you might be making a noticable dent in their profits for keeping the sail. You can never go wrong doing what you did though as far as i'm concerned, it's the safest bet. Good job.