I think it really sucks that a lower a arm got lost and it not being your fault but they are aftermarket parts that are dicountiuned that you bought used and now sold. Sucks you can't get a replacment for just that one arm but before this turns into a "screw alba" thread I would see if alba would be able/ willing to make a similar set of lower arms for you, or possible make a newer style replacment same geometry lower arm that will work. Even if it has four gussets instead of two Maybe see if Tyson racing or some other fab shop can take copy the desing. Best of luck with it really suck when stuf like this happens