It's possible to retrieve the vhdl code from the .pof file? if so, how?

For all practical purposes, no. Not possible.

Theoretically if one knows the exact encoding of a .pof file for a particular device, one could write a disassembler that built a gate level connectivity list of logic cells. And that could be represented in VHDL.

But .pof file format is not public information. And the generated VHDL netlist would be a full chip gate level netlist. Not so useful.

So if you have a .pof file but lost the source VHDL you are out of luck.