Empty box, hey?? Okay, a couple of details here; was your vendor a private seller or a dealer or salvage yard? What rating or degree of confidence was listed beside the vendor name on the site? Under the seller name was there a link to contact the seller? Is this seller still listed as active on the site?
Speaking only for myself here, I have had occasion in the past to contact sellers about items or parts that I am interested in buying or wish to know more about. The contact process goes through E-Bay and you have to be logged on or signed in to them to reach the vendor and send a message.
In the last half-decade or so, E-Bay has become seriously paranoid about establishing and maintaining the reliability and credibility of its vendors. The administrators for that site take complaints very seriously and will contact you as the plaintiff to make absolutely sure you want to file and prosecute your grievance because once it becomes a matter of record it is permanent. Before, vendors who received down-checks against them for problems related to their sales history could work them off by being and staying "clean" for a specific length of time. Now, no more. Any negative results, beginning with the initial complaint being filed, to it either being dismissed or confirmed, now remain as part of the vendors permanent record. Multiple complaints get the vendor dumped; ejected or evicted from the site. There are stories of black listed vendors trying to get back in under a different name or alias but the vetting or acceptance process has become quite thorough and "sneakers" tend to get caught sooner or later.
I wish you all the best and hope that vendor just made an honest mistake during the shipping process, and that you get a second package or box with your carburetor in it ASAP. Unfortunately there are scam artists out there and they can and do sneak under the vetting fence from time to time.
Nick