Why would a guy who was treating me nicely yesterday ignore me today when I said hi to him?

we had very good conversation for some days. i think we became friends but now he is ignoring me. i think his friends teased him about me. i don't have crush on him and he too. but i feel pain bc i lost a friend who was really nice to me and our thoughts and personality was very similar. why suddenly he ignored me?

Why would a guy who was treating me nicely yesterday ignore me today when I said hi to him?
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