There are two possibilities here -

1. The log will be captured in the Gallio test results report and will end up in the test output (similar to Debug.Write and Console.Write), though likely at the bottom of the output and not synchronised with the rest of the output
2. It will land in a unmonitored buffer that will be deallocated after the test run is completed with no way to access it (i.e. it's swallowed).

If you need to get output from your tests, I recommend using Debug.WriteLine or Console.WriteLine, perhaps from behind some kind of interface or facade so that you can direct the output elsewhere if you need to. This is the widely accepted way to output data from test code and will work for all test frameworks.