If I send a secret to you in the post, and you put the envelope in the recycling unopened, have I disclosed a secret to you?
They might have put the envelope in the recycling, but they never have it emptied and someone just told them it contains a £20 note.
People seemed to be reacting as if every website an O2 customer visited was going to add their phone number to their files, and that's not the case.
Yes. Intent and the fact you did it is what matters here.
Oh god yes. Everyone who reads your comment is hoping you don't work with financial, personal, confidential or (eek) classified information.