Is it as easy as retracing your steps through the trees? There isn't really that much ground to cover and if you keep checking your radar you might pick it up. If it's dropped that is. If you sold it (I don't think you CAN you sell it???) then check Fuzzfas and Madras. You obviously haven't merged them already, and since you are sure it's not still hanging on the tree, and it is not in Party items or personal items the only other option is that it is lying around somewhere waiting to be rescued.
There is no other way into the 6th bough. Not yet, anyway.