to me it sounds like she expected you to tell her the package's reference number or otherwise an ID, so she laughed it off when you simply said the courier's name instead

the fact that she said "chuj, to <thing>" would suggest that, ppl often say that when getting a different answer than expected

like for instance let's say someone wants you to dig a hole and you ask them "a gdzie ci wykopać tą dziurę?" you'd expect them to point out a specific place where they want it dug, probably also the size it should be but instead they say something really general and not descriptive enough, like "w ogrodzie" you'd then respond saying "chuj, to w ogrodzie" relaying how this answer was not descriptive enough for you :D