Not via the API, not yet at least. You'd have to uncover the XML structure it lives in and go down to the lxml level and perhaps XPath to find it. Something like this might be a start:
body = doc._body
# assuming differentiating container element is w:textBox
text_box_p_elements = body.xpath('.//w:textBox//w:p')
I have no idea whether textBox is the actual element name here, you'd have to sort that out with the rest of the XPath path details, but this approach will likely work. I use similar approaches frequently to work around features that aren't built into the API yet.
opc-diag
is a useful tool for inspecting the XML. The basic approach is to create a minimally small .docx file containing the type of thing you're trying to locate. Then use opc-diag to inspect the XML Word generates when you save the file:
$ opc browse test.docx document.xml
http://opc-diag.readthedocs.org/en/latest/index.html