As soon as you type an "A" in column A, row 11 of "Results" sheet, you should see column F show "A_4". This means this is the 4th occurance of "Item A", and therefore it should add a 4th row to the Item A sheet. It should not overwrite anything.

My sample is assuming you are adding new rows in the results sheet (even for same Item). It does not assume you are overwriting previous information.