Another quick, self-contained way. From the shell, run:
Unknown.exe /AutoIt3ExecuteLine "MsgBox(0, 'Result', 'Probable AutoIt executable found.')"
Note that this will fail if ever the script is purposedly compiled with option #NoAutoIt3Execute OR give a false positive if the program is sneakily written to accept the same arguments while being coded in some other language. Both odds are IMHO fairly safe.