Its possible just incredibly hard for somebody who doesn't know how.
i though so
Yes very possible, and Very hard, there is numerous 3rd party applications that run a host of tools just to unpack it, including but not limited too, Hex addresses, Memory dumps, hex editors , etc. etc.
it is possible to unpack themida packed .exe files for reverse engineering. however it is not possible to unpack a themida packed .dll file for editing, the file would be corrupted and rendered useless.. sorry