Grimrock

So as i started getting into the game i acknowledged that all the scrolls are just hints, so i've cleaned my inventory out of them. Later i found out that on this level 4 you need all 4 scrolls to advance so i began to search for them all over level 4 and 3 but i found only 3 of them. Don't want to restart the game so please, if anyone can help me? Please don't say "have you looked in boxes\bags etc." because i've done it.

This might be trivial, but where did you empty your inventory? If you remember, go back to that place.
Also, are sure you have got all 4 scrolls before? Maybe you didn't complete all 4 puzzle rooms and that is why you only found only 3 scrolls.
Last resort is returning back to an older save.

There may be some other way to resolve it (maybe with debug mode or something), but I don't know about that.
But even if you do have to restart, it's not such a big problem, as you now know what's what and where things are. So you should be able to advance fairly quickly. You may even get a head start by building your characters more appropriately.
Good luck!