1 "不就" ...."吗" change a statement to a question, means it is not a big thing, don't be so frustrated. 你被人踹了。---------你不就被人踹了吗？ 我迟到了一分钟。-----我不就迟到了一分钟吗？ 2 被 is a kind of passive mood, so the verb is act on the subject. In this sentence, "you are been throwed away". The other one end the relation without your agree. 3 Add one point about "不就是", here it is same with ”不就"here. However when ”不就是“ connect with noun, which means that only one verb “是” in sentence, the sentence emphasis "just that noun". 这不就是你的车吗？-----这就是你的车, this is just the car belong to you. 你不就是我要找的人吗？------你就是我要找的人, you are just the one I want to find. And here, it can't use "不就“。

被人踹了 or 被人甩了 is the same thing. 踹：kick 甩：swing/throw if a person say “我被甩了” or “我被踹了” it means his/her girlfriend/boyfriend break up with him/her. it is his/her girlfriend/boyfriend who decides to break up, not him/her. “你不就是被人踹了吗？” this is a question with "不就是" this is a question but in fact, it means "not a big deal" because of “不就是” so this phrase means "she/he broke up with u? its not a big deal man, relax, forget her/him come, let's go to drink." something like this. a question with “不就是” is useful. if u want to express that something which is regarded as a very important thing by someone but u dont think so, then u can use “不就是” for example, Bob works with u. he is older than u and he has more experience than u about ur work. so he always blame on u if something wrong. then u can say "你不就是比我有经验吗？难道你就没有做错吗？" u see, “你不就是比我有经验吗？” Bob thinks that it is very important that he has more experience, because of this, he thinks he can blame everything wrong on u. but u dont think so. u think having more experience is not a big deal. so u can say "你不就是比我有经验吗？" to Bob to express ur dissatisfied emotion.

被人踹了，指的是被人甩了，由于很多原因分手是方提出的。 不就......的：是指仅仅。 这朋友觉得他被甩了没什么大不了的，也是变相安慰。

one more thing: 不就是 = 不就 here. so 你不就被人踹了吗？ = 你不就是被人踹了吗？ forgot to tell u this.. :D

大概就是与被人踹了，那种样貌一样。其实朋友也不想解决，只是觉得自暴自弃很难看。说这样的反话，以为会有激励的效果。很熟悉的耍酷场面。。。