Well, if you don't get any response if the contact is truely offline, I smell a rebuild of block checker.
If you are desperate to find out whether someone has blocked you, you can actually find out if they blocked you, if you keep on changing dp and everything else that might trigger a response at the other contact's wlm... I mean it's like fishing, they have to bite once...
You could even track your contacts for opening a session (especially if so many things can trigger a response) and if they do respond, you know you've been a bad boy
Not that I have many people blocked me or something, in fact, everyone who blocked me i have blocked first at the moment, but sometimes people block everyone to talk to just someone, like with my PlusPrivacy script, and if that happens often it's time to think whether you realy are a good guy, just for knowing...
And it would give you a feeling like "yes, I know more than others...", which, be honoust, is what we all want, some more than others...