If I loose on a bid, i'll contact the seller and ask if he or she has another one and they usually sell me another of the same item for the same price that was won with or i'd pay a little more for it, but it depends on the seller if it's a retailer.
I use Kadee #58, 158, and 118's on my cars, but I have begun to use the Sergent type-F's on all of my locomotives, since the the Sergent type-F's don't couple properly with any other brands of couplers.