How to save DOM references of elements whose parent innerHTML property was set to empty string (in IE)

How to save DOM references of elements whose parent innerHTML property was
set to empty string (in IE)

In IE, when one sets the innerHTML property of a DOM element, this
automatically empties the innerHTML property all the child references. How
can I keep the child in memory in order to be able to clone it later and
append it to the parent?
Example HTML:
<div id="parent">
<div id="child">
</div>
</div>
script:
var parent = document.querySelector('#parent', document);
var child = document.querySelector('#child', parent);
parent.innerHTML = '';
// at this point child.innerHTML is ALSO empty!!!
// I want to clone later the child back into the parent
How can I keep the child in memory? Is child.outerHTML the only solution?
PS: in IE (up to 10), no jQuery