I'm not a 100% sure, but won't
$(data)
produce a jquery object with a DOM for that data, not connected anywhere? Or if it's already parsed as a DOM, you could just go $("#myImg", data), or whatever selector suits your needs.
EDIT
Rereading your question it appears your 'data' is already a DOM, which means you could just go (assuming there's only an img in your DOM, otherwise you'll need a more precise selector)
$("img", data).attr ("src")
if you want to access the src-attribute. If your data is just text, it would probably work to do
$("img", $(data)).attr ("src")
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