Don't assume that because he hasn't called he is avoiding you. Since you don't know him there could be a list of reasons for why he hasn't called. Calling him will make you look obsessive so I wouldn't do that. If it is meant to be then it will happen. There is a good chance that he is interested if he returned your contact initially. I would just wait to see what happens. You have nothing to lose. You didn't have a relationship up to this point so if it works out great. If not then you haven't lost anything. I don't think you blew it. You reached out to a guy you liked. So what. You have nothing to lose by trying. The worst that can happen is you go about your day at the office. It is okay to try and fail at a relationship. Don't be so hard on yourself. It's okay to ask someone who doesn't like you back. Have patience.
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Thank you. I agree with your advice. But may I contact you again in a couple days?