"I forgot to write to you about Caesar; for I see what sort of a letter you have been expecting. But he wrote to Balbus and told him that the whole packet of letters, in which were mine and Balbus's, was so soaked with water when he received it that he did not even know there was any letter from me. He had, however, made out a few words in Balbus's letter, to which he replied in the following words : "I see that you have written something about Cicero, which I could not understand, but as far as I could conjecture, it was the sort of thing that I thought more to be desired than hoped for." So later on I sent Caesar an exact duplicate of my letter." (Ep. ad Quint. Frat. 2.12)
There are a few interesting incidental details that reveal the problems associated with letter writing. First, there was an entire packet of letters delivered to Caesar all at once. The phrase in Latin here is "fasciculum ilium epistularium," which is just referring to a packet or parcel of letters. It seems to imply a loose bundle of individual leaves rather than anything that was bound together like a codex. One can infer that these letters, though written likely over a span of several days, were delivered to Caesar at one time, indicating that it may have taken some time to deliver them.
Second, the material, either papyrus or parchment, was damaged by inclement weather. Either the pages were so stuck together that they couldn't be separated and the writing made out, or the ink had been completely washed away by the rain (or likely both). This reveals the precarious nature of the material written upon. It is a miracle that there are any documents that have survived from the ancient world at all.
Third, this side note by Cicero reveals that a common practice was for letter writers to keep a duplicate copy of their correspondence on file for just such a circumstance. Cicero was able to make another copy of the letter and re-send it to Caesar.
Finally, this anecdote presents an example of social networks preventing the loss or corruption of texts. In this instance, it was not the deliberate alteration or misuse of a written text that was being guarded against, but the loss of text through damage by rain and moisture. It looks like Balbus, upon receiving his reply from Caesar, notified Cicero that his letter to Caesar had been damaged and lost and Cicero was able to re-write the letter and thus allowing the transmission of the message or information to be completed.
This example brings together a few themes from the ancient world that often surface. First, that the written material was highly volatile and susceptible to environmental damage or loss (such as this example from Arsinoites in Egypt during the first and second centuries AD). As in the story of the worn archival documents at Arsinoites, the only insurance against the loss of these documents was in having duplicates of these texts, in this case, the duplicates of Cicero's letters. And second, one aspect of this preservation against the loss or corruption of texts was through social networks guarding against this loss.
Cicero, Letters to his Friends. M. Cary trans. LCL. Vol 3. Cambridge: Harvard University Press, 1960. Page 523.