I don't think it is cut and dried either way.
If you analogize to a supermarket purchase, as soon as one person (potential buyer) puts an item back, any person should be able to pick it up and buy it under the same terms. That makes it look like Tuffy should get it.
If you analogize it to some types of business deals, the item often cannot be marketed or sold while the offer is pending, and only after the offer is rejected can a new offer be tendered or accepted. In that instance, Tuffy's provisional "I'll Take It" would have no effect and Comeaux gets it.
Fortunately, for those involved, cooler heads have prevailed. Going forward, best practices would be to either remove or expressly allow provisional "I'll Take It" in the Terms & Conditions of each sales thread.