The word "ditch" meaning to leave someone or get away from someone is more of a slang word. If you're in a professional or polite conversation you wouldn't use it. It's a word commonly used by kids. "Hey, let's ditch Bobby" this means "Let's get away from Bobby so he can't find us" if they are all riding bikes and Bobby is behind them.

You don't have to be in a romantic relationship with the other person. However it does have connotations that you are somewhat familiar with the other person. So using it for a random stranger might sound a little odd. But you would say that you "got stood up," or "he/she stood him/her up." You wouldn't say "stand up." The only time you I can think of is if you told a person, "you better not stand me up."

You would say "You stood me up". If someone makes a promise or an appointment to meet you at a certain time, then it appropriate to refer to that as "being stood up". But beware, if you say this to their face it is very direct/forward and can sometimes be seen as rude if you do not know the person very well.

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