in Sevcenko ..

"In 1868, the Russian Ambassador to the Forte Ignat’ev, who did not mince words, alluded to Tischendorf’s proposed scheme and said that the “ misunderstandings ” connected with the Sinaiticus were created by “ a German who had wanted to take another joyride to Sinai and Athos at the Government’s expense and under the Russian flag.” (45)

(45) Ignut’ev to Archimandrite Antonin, June 30, 1868, (as in note 6 supra), p. 27.
in Dmitrievskij, Graf Ignat’ev... p. 68

New documents on Constantine Tischendorf and the Codex Sinaiticus -(1964)
Ihor Sevcenko

.. was it possible that Tischendorf, or people working with him, snuck in a "joy-ride" to Athos?

Remember, Simonides ended up in St. Petersburg, after his faked death, and this was only discovered accidentally.