How to deal with your teacher who took your phone?

So my PE teacher in college took my iphone saying that he is going to conference and he is ashamed to use old nokia in front of others. He said he will return it few hour later but he didn t. He didn t came to college few days after that and when he came he lied to me that he left it at home far away from city. He said he will give me back next wednesday but today he said that he was busy and he will return it later. Now I thinking about reporting him to college administration but if I will he might lose his job. What should I do?

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