Keep looking and don't put all your eggs in one basket. If they didn't respond, they probably don't like the offer. Shift your attention to looking at other homes and if it comes back around to you then that's great, if not, you are not waiting by the phone. (I'm assuming you've tried to get an answer from your agent already.)
If you put in a very low offer they may not even acknowledge it. Just see if the listing agent did indeed receive it and if so, then maybe she or he can clue you into what is going on with the property/sellers.
If I can be of any help please let me know. :)