It would have a hard time working it's way out Tim, but even if it did there would not really be a problem per say. The RW is not really the life support, the hitch underneath it is. The hitch would bind up tight and might be rough to descend on but that it why we carry 8's or use munters.
I guess that is another major strength of the Rope Wrench; that it allows climbers to operate the same way on a single line as they used to on a doubled line, with regard to being able to use a hitch, and also still being dependent on it for life support.
The idea of the Rope Wrench was absolutely a stroke of genius.