英文句子結構問題

Hi,
I got my bag back which was hidden by Mary in my/the classroom.( original sentence)
Something wrong in this original sentence!
" which was hidden" should be used to decribe " my bag",
NOT " back".
One example for you:
1) {The man<---- who has a notebook in his hand } <- Subject is my father.
" man" is followed by " who".******************
Corrected sentence:
I got back my bag<--- which was hidden by Mary in (my/the) classroom.
man <------------ who
my bag <--------- which......
Now we know the correct answer to this question is
***I got back my bag hidden by Mary in ( my/the) Classroom.***
"hidden" is a simplifed version of " which was hidden.( Passive voice)
If you take a look at the parts in colors, you will understand it .

Good luck!
Bye for now.

My suggestion:

I got my bag back hidden in classroom
理論上你可能沒有錯，但看起來不順。如果將句子修改一下（如下），看起來便順很多。

I got back my bag hidden in classroom.

Hope it helps!

By deleting the "which", it made the hidden without a connecting word.

Moreover, the main point is the "Bag", therefore, I suggest the following:

The bag hidden by Mary in the classroom was returned to me.