The sentence should have better written as, "So the laptop you brought last night to read all about Serena, was not yours."

With Present Perfect always seek a connection to a present situation. In this case, the action took place in the past "last night", but the conclusion "you've been to" is related to a present situation. You can probably find counter examples for most grammatical rules, this does not mean that the rule is wrong. Keep in mind that grammar rules are about the most common language uses. Nine out of ten times, you cannot go wrong using proper grammar.....

Jenny: So that wasn't your laptop you've been to last night to read all about Serena van der Woodsen. This sentence is bad. It should read: Jenny: So that wasn't your laptop you were at last night to read all about Serena van der Woodsen.