Can't drain water to outside faucet

I have a faucet right outside of the garage. This faucet is connected to a water pipe with shutoff valve inside the garage. Before each winter, I shut off the valve and open the faucet to drain out the water. However, when I shut off the valve and open the faucet outside, no water comes out. Not a single drop. I am assuming this means that water is full inside the water pipe. As a result, every winter, the pipe will come off right below the shut off valve. My guess is that as the water freezes from outside, it had no place to expand and as a result, pipe simply comes off from the join that connects the pipe to the shut off valve.
To resolve this issue, I asked a plumber yesterday to re-do the pipe line with new shutoff valve. He also installed new valve with drain cap. He told me that way to drain water is to shutoff the valve first, open the faucet outside and then open the drain cap. However, when I followed these steps, no water came out. Not a single drop once again.

I am afraid that it's just a matter of time before the pipe comes off again near the shutoff valve. I even installed water pipe heat cable near the shut off valve. However, I am afraid that as water starts to freeze near the faucet, since there is no place to expand, the joint near the shutoff valve will come off again.

One this, i have 2 questions.
1) In this case, is it better to leave the shutoff valve open? I am thinking that since the most of the pipe won't freeze due to the water pipe heat cable, by opening the valve, it will have some room to expand if needed.
2) The pipe with shutoff valve is about 6 feet long. The vertical pipe is connected to smaller pipe (~5 inches long) which connects to pipe with faucet on it. This connecting pipe is pitched slight down. Can this cause water to not drain?

With temperates in below 0 in my area these days, I badly need someone to tell me how to prevent my pipes to break again. Thanks for your help in advance!

Post a picture of the outside faucet.
It may have a vacuum breaker on it and it is not allowing the water to drain out properly.
If you do have a vacuum breaker on it then remove it if you can or pull down gently on a little plastic pin at bottom of vacuum breaker and that should let water out until you let go.

Thanks for a quick reply. There is a vacuum breaker and so I pushed it up the plastice pin to let the water drain. However, even after this, no water came out. For now, should I just leave the shutoff valve open so that there is at least some room to expand? Again, my pipe has heat cable so entire pipe won't freeze.

Yes leave it open
Also you gotta pull down the pin not up.
And the other thing I can think of is make sure the rubber washer on the cap of the shutoff valve comes off.
Sometimes you screw the drain down cap off and the washer is still stuck on the valve.
Hope this helps