Forgive me my pedanticism, but you're using the word "theory" incorrectly, from a scientific perspective. In science, a hypothesis is published and IF the hypothesis withstands scrutiny (i.e. a lot of testing) and IF the hypothesis provides a generally acknowledged useful way to model physical phenomena (especially to predict additional behaviors not known when the hypothesis was proposed) THEN and ONLY THEN does a hypothesis become a theory.
This is important! For example, when Creationists say "evolution is only a theory" they are almost right ... evolution is a fact that is explained by the Theory of Evolution (i.e. natural selection), which has withstood more than a century of close scrutiny and provides the best explanation of observed phenomena. Similarly, gravity is a fact that is explained by the Theory of Gravity, etc.
I bring this up because scientists often assign a strict meaning to many words that most of us use quite loosely in daily conversation. We read of "legal theories" here, and watch detective shows where everyone has a "theory" about what happened. Scientific theories are a whole different critter, perhaps more akin to a "legal theory" that's made it all the way up to a unanimous validation by the Supreme Court.
" ... and, apparently, they didn't even ask for the proper postage from the recipient, which is a little odd ..."
This isn't odd at all. Note that the stamps are Egyptian (if, in fact, they are real stamps.) Postal services generally deliver mail from one country into their own country without charge. That is, the originating country sets the rate and collects the postage; the assumption is that mail is seldom one-way, and there will be a roughly equivalent volume of mail heading in the other direction.