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I came into a sudden question!

I was talking to my friend on the phone. He is coming tomorrow by express bus. The bus departs at 10:50. I asked him "what time will you step out of the house?" He said "about 10:20?" I definitely thought that's impossible to get to the bus terminal. I said that you should get out of home at least 10:00. And I said to him

"If I didn't tell you about this, you would miss the bus."

Is it right? / I don't think this situation is past-perfect subjuctive because catching the bus will happen tomorrow(not happened yet.)
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Hi Moon;

This is a mixed conditional, where the time of the if-condition is in the past, and the consequential action is in the future. There are various combinations:
past -> present
past -> future
present -> past
present -> future
future -> past
future-> present

This is a good reference with examples of the combinations.
http://www.englishpage.com/conditional/mixedconditional.html
Comments  
I would say:

"If I hadn't told you about this, you would have missed the bus."

This is complicated. First, this is a conditional (if, then) form. You are taking about an event that didn't occur. So use the subjunctive form. You are also imagining yourself looking back at the events. So the whole action is in the past.

If you want to look forward, you could say something like:
"If I don't tell you about this, you will miss the bus. Friend, you must leave earlier than you plan."

But in this case, you are preparing to tell your friend something which you then tell him.

Does this help?
Students: We have free audio pronunciation exercises.
Thank you very much for your detailed answer.

Like you said, the situation seems complicated.

You mean, the expression for it should be a past perfect subjective from even though taking the bus is the following day's event from the time of the phone call.

I think it makes sense; I applied the situation to my language. It sound like a situation that already happened and a situation that yet to happen is the same.
 AlpheccaStars's reply was promoted to an answer.