Ok, Bart Ehrman wrote about it, so it might be a straight pen.
This is on his blog:
Tischendorf and the Discovery of Codex Sinaiticus
Bart Ehrman - June 12, 2015
You have to join (e.g. trial is $4 for one month) to see the whole post.
My comment, 5/14/2016 which is currently awaiting moderation is:
It seems odd when any scholar today (and there are many) writes about Tischendorf's 1844 story as if it were an historical and factual account.
The recent article by Nicholas Fyssas in the 2015 "Codex Sinaiticus: New Perspectives on the Ancient Biblical Manuscript" book said:
"These observations may also urge us to take with some reservation Tischendorf's claim that be was allowed to take the forty-three folios."
However, the situation historically is far worse than simply "some reservation".
Even back in 1874, the top Scottish scholar James Donaldson wrote:
"There are many circumstances in this narrative calculated to awaken suspicion"
When Tischendorf wrote his family correspondence, (we have extracts recently published) he simply wrote of the 43 leaves as coming into his possession, which should be seen as thief-code for "I heisted the leaves when nobody was looking". This matches the Porfiry Uspensky account of the state of the ms. in 1845.
We might also note that the "phenomenally good condition" of the leaves, as described even today by Helen Shenton of the British Library, made it possible to transport the leaves surreptitiously without difficulty or special handling. We might wonder whether such "exceptional" condition (Gavin Moorhead of the British Library) is consistent with the history of the manuscript that has become today's Sinaiticus science.
Some of the information describing this 1844 history, with the url to the family correspondence, is at:
1844 saved from burning myth - "ich bin in den Besitzgelangt von"