How to make a request with the word "if"
If I'm not mistaken, I sometimes hear people say like the sentence below to make a request.

e.g. If you put this in your bag?

I think this sentence sounds a bit truncated, but does it sound natural or did I hear wrong?

Thanks.

Question

How to make a request with the word "if"
If I'm not mistaken, I sometimes hear people say like the sentence below to make a request.

e.g.  If you put this in your bag?

I think this sentence sounds a bit truncated, but does it sound natural or did I hear wrong?

Thanks.

Answer

No, it doesn't work as a request. It can be used to query an outcome(if this, then that) in the context you have supplied.
A request would be "Could you put this in your bag?".

Answer

If it is in a context of a request, you might have heard

If you could put it in your bag...            (note "could", and no ? or intonation of questioning)

(For example, at a stored you may say "if you could put it in a bag", which is a request)

It is an indirect form of a request, meaning

If you could put it in your bag  (I would really appreciate it).

It's similar to a Japanese sentence ending with "...なきゃ", which means the other side understands it implies ならない and the like is omitted after it.

Answer

I think you heard wrong. Anyway we can make request using 'if'. See an some examples. .
 1.  It will be great help if you give me 1000$.
 2. It will be great help if you tell her that where I am?
2. It will be kind of you if you let us to go.