Has anyone found the sub with an underwater camera/rover yet?
Yes.
Yes.
In 1963, a deep-sea diving bathyscape, Trieste I and II, “recovered some remains of the ‘Thresher’ submarine which sank off Boston. The sub was first discovered and photographed by ‘Mizar,’ a naval research ship which towed an underwater camera platform.” Link: http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/6154/SPUMS_V7N3_9.pdf?sequence=1
Here are some photos of the search by Mizar:
http://www.history.navy.mil/photos/sh-usn/usnsh-t/ssn593-k.htm