How do you respond to someone who has stood you up?

How do you respond to someone who has stood you up? Most likely for the purpose of seeing how long you will wait for them? It's been two days and no apology and I haven't tried to talk to him yet but he needs to know it is not cool.

PS - He made me wait 4 hours.. when I was supposed to be with him at work. I know he got swamped but he still could have picked up the phone.
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Thanks for the replies! It sucks because when we were together just before he ditched me we were having a fun time, play fighting and what not..
How do you respond to someone who has stood you up?
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