This question was posted a long time ago and the issue has probably been resolved since. Anyway, since it's quite on top on Google, it deserves an answer...
SoapUI turns off logging during the load test (and probably other test items as well) as all the messages could be overwhelming and decreasing the test performance. What it literally does is calling the following on the groovy logger:
log.setLevel(Level.OFF);
After a test item finishes (project, test suite or test case), logging should be turned on again. But it looks like teardown is called as soon as the last sub-item has been started (at least with the load test), but at that moment some time demanding test might still be running, so the teardown log won't be visible. In order to turn it back on already during teardown, you only have to set the level to INFO again at the beginning of the teardown script:
log.setLevel(org.apache.log4j.Level.INFO)
Note that log entries from the still running test might appear as well, since the groovy logger is shared accross groovy scripts.
See similar question for more...
