Is it correct to say, "I lost my bus," when you miss a bus? I have seen it commonly used.
Certainly not in American English. I've never seen it when reading British books, either; in fact, I don't recall seeing or hearing it in my life.
If I were to hear it, I'd assume lost meant "misplaced" and were meant as a joke.
On the other hand, the questioner's profile says he's Indian, and I don't know Indian English at all. Perhaps this is common there, though Google seems to imply otherwise.
Edit: Others' comments on this answer indicate that this is considered incorrect in both the U.K. and India.
It is more appropriate to use missed my bus. I've never heard people say “I lost my bus” to imply the meaning you are referring to. I think it can be used in situations when a bus once owned is destroyed, but that is rare.
I fancy that this sentence is from a story where the speaker runs some transport agency and the bus service he/she had run earlier is terminated or is out of his/her control. :)
Well, I've listened the expression to lose the bus in America, I was talking to my friend and he said to me: tomorrow, don't lose the bus, don't miss school. It was interesting that he used both verbs. PS: He is American, born and raised in Kansas. Maybe it is some Portuguese or Spanish influence on his speech, even tho there are few immigrants here. Maybe it's starting to be interchangeable just like miss/lose an opportunity.