As some theorized, this did turn out to be the work of "Ravenbar" (real name: Paul, from Guam) on Ebay. After several days we were able to get in touch with Paul, who confirmed with us on Saturday that this was, indeed, his work, but that he did not know how it had gotten to us. Paul contacted us late yesterday to let us know that he had just received a letter (originally we were baffled as to how he got mail on a Sunday, but then we remembered time zones exist) from the USPS sorting service in Honolulu, HI (from a guy who, coincidentally, is also named Paul) stating that the outer package of something he had mailed had been found without its contents at their facility.
According to Paul, this package was en route from him in Guam to his intended recipient IN ITALY (registered mail confirmation attached) when it must have fallen out of the package in Hawaii. Our address had originally been put on the manila wrapping of the journal just for cosmetic effect. We believe that the post office wrote on our Zip code on the outside of the package and, believing the Egyptian postage was real, sent it our way. From Guam to Hawaii en route to Italy with a stopover in Chicago: truly an adventure befitting Indiana Jones.