I sent the proposal but I never heard back from the client

The prospective client approached you.  They seem to really like what you have to offer.  
They ask for a price.  
You draw up a proposal.  It takes hours, full of detail on how you'll deliver this amazing project to them.  
You send it to them.  
They go quiet.  
You never hear from them again.  

Why is that?

It's because clients only want to hear three things from your proposal.  

Do you understand what I'm looking for?

Is what you're charging worth the outcome I'll be getting?

Is it a big risk in hiring you?

So when you're talking to the client, you have to find out what they will expect to see in their proposal.  How do they want you to answer those three questions?

And then that's basically all your proposal needs to say.  

My proposals (for which I get an 86% close rate) are 7 pages long and never include any technical details on what I'm going to deliver.  I got so good at it, I even wrote a book about it.  

However, there is an alternative.

If you choose to focus on a particular type of client, you can do all that research upfront.  Find out what they (as a group) are looking for.  Discover how much they expect to pay for it.  Learn how they've been burned before.  

And then instead of writing a proposal every time, you can just send them to your sales document.  

It makes it easy for the client to choose you and saves you time as well.