Translation:Sofia searched everywhere, but could not find her friend.
Well, I was asking why ĉien is not in the accusative. The search was performed upon everything. Just like saying "mi serĉas vin".
The accusative shows the direct object, so it shows WHAT Sofia is searching. "Everywhere" indicates WHERE sofia was searching and not WHAT. Correlatives finished in "e" just are used in the accusative when they indicate direction.
Mi ne povis skribi la lastan vorton ĉar ĝi mi ne povis vidi kaj alklaki ĝin. Ĝi estis en tria linio.
I'm probably gonna start a bad thing here but... The pronoun is "sia". So, in this sentence, there wasn't any grammatically correct way to use a gendered pronoun to refer to "Sofia". I had to understand that Sofia is a woman in order to correctly translate the sentence into English. I just really wanted to point that out, it just seems noteworthy for whomever it may concern.