The particles of many phrasal verbs, especially phrasal verbs that relate to physical movement, are frequently used alone with a form of be. This is very common in conversation when the verb already been stated at least once and does not need to be repeated:
Customer: Have you run out of coffee?
Store clerk: We're out of regular coffee, but we're not out of instant.
Marsha: When do you have to move out of your apartment?
Nancy: I have to be out by next Wednesday.
Jim: Did you turn the air conditioner on?
Bob: No, it was on when I came in.
Mother: Has your sister woken up yet?
Susie: No, she's still not up.
Using the particle without a verb is also common when a phrasal verb can be understood from the context. Sometimes, only one verb is obvious:
Raul: Are you through?
Todd: No, I won't be through until after 4:00.
If this conversation occurred at a place of employment, the phrasal verb could only be get through. But ofter, in a particular situation, more then one verb might be understood, but to the speakers it is not important or necessary to be specific about which one:
Carlos: Is Karen in?
Paul: No, she isn't.
If this conversation occured in an office building, several verbs might be understood: come in, go in, get in, (be) let in.