What does “could have + past participle” mean?
"Could have sworn" is used when someone feels sure about something even though it appears not to be true. In this case she was sure where the hive was but it is not there. Ex: I could have sworn I’d paid that bill. Ex: I could have sworn that I left my keys here. We generally use could have + past participle when we want to make a guess about something that happened in the past. This is used when we don't know if what we're saying is true or not true. We're just talking about our opinion of what maybe happened. Ex: A: Why is Kate late? B: She could have forgotten we were meeting today.