looks like it may have a couple of jagged bits of the screw protruding (particularly @ 1 o' clock in your second picture). maybe you can soak in wd40 and attempt to turn it with a small screwdriver against the protrusion.
I'm not sure of the exact titanium alloy used for the frames but the thermal expansion of titanium is around half that of stainless steel. If you are looking to have the frame refinished then you could try heating the area with a torch and then rapid cooling a few times to try and break the screw loose. I know you don't have much of the stuck screw sticking out to work with but as a last resort it may be worth a shot.