There is in effect a gap in the contract. The gap would be filled in by the court with a reasonable term, using as guidance what the parties would have provided if they had anticipated this situation. Compare the Parev Products case. The parties probably have a good faith obligation to agree to a substitute arbitrator unless it is clear from the circumstances that they intended no arbitration if Rev. Lovejoy was not available. Baseballs are goods.
Advertisements are generally invitations to make an offer.
No express warranty is part of the contract. The implied warranties are effectively disclaimed. This question did not count, but it's pretty amazing.