stolen macbook - logging in to my icloud on another mac

Hi there

Today my macbook air was stolen and I'm trying to retrieve my data from my icloud. If I log in to my icloud on a friend's mac I have to agree to delete all calendar entries. Will those reappear automatically once we sign back in with the original account or will all the entries be lost?

a quick answer would be highly appreciated, thank you so much!!!

Susan and Anita