Is it possible to retrieve a previous un-evaluated, un-normalized input?

Edit: See here for a better answer.

Just a slight modification of Mechanical snail's answer here, (I need a more creative username...) to make the output match the input exactly.

In[1]:= {{2}, {3}} // MatrixForm

In[2]:= ToExpression[InString[1], StandardForm, Defer] // DisplayForm

Which you can copy/paste, or just append //CopyToClipboard to the command above and you can just paste it and use it. This will work with other automatically parsed expressions like 2+3 as well.

I don't think it is possible by reading the In, since the information is stored in a list of HoldPattern expression, and your input is not preserved. But if you did not delete the input cell, it is possible to obtain your input by doing this:

CellPrint@
Cell[Cases[NotebookRead@Cells[], 
Cell[x_, _, _, CellLabel -> "In[42]:="] -> x][[1]], "Input"]

You can get exactly your input in a new cell.

Another idea is to CellPrint the InString output:

reprintInput[n_] := CellPrint @ Cell[
    BoxData[ToExpression@InString[n]],
    "Input"
]

For your example:

$Line=41;
{{2}, {3}} //MatrixForm

Then, reprintInput produces an exact copy of the original input cell:

reprintInput[42]

{{2}, {3}} // MatrixForm

If you just want to store an unevaluated version of the input somewhere, you could use something like:

input = ToExpression[ToExpression@InString[42], StandardForm, Hold];
input //InputForm

Hold[MatrixForm[{{2}, {3}}]]

This is similar to @JasonB.'s answer, but there is no need to use copy/paste.