I’m trying to imagine how it could possibly be a GOOD sign. And I hope you propositioned him via email or phone, because if you asked him in person and he just silently backed away, I have awful news for you.
If you’ve made it clear to a guy that you’re interested–and he’s interested–ten it’s very rare for him to fail to take advantage of that at the earliest possible opportunity. Even a shy guy will usually make a play if the field has been cleared for landing.
If it’s over email, you’re stuck in the classic conundrum of sort of hoping that the guy you like has undergone a terrible misfortune that’s prevented him from getting back to you (nothing too nasty, of course).
Because otherwise, he may have already relegated you to the spam folder of his heart.