Are you sure that you don't have a tilde? On my A1200, it's a dark grey button on the top-left, just under escape (not where you'd expect!)
If all else fails, just open the drawer where it is and right click and select Window -> Show -> All files. Then double-click on the icon, and there will be a box with the name already in - just add "lha x" etc. Or just rename the file :-)