I think so, too. I imagine the vast majority of successful cases do not get reported.
It all depends, too, on how liberal you are with the definition. If you go to the
Wikipedia page on this topic, you will see a nice list of the different formal protocols that can be used. Scroll to the bottom of the page and you will find this paragraph:
Although in-water recompression is widely regarded as risky, and to be avoided, there is increasing evidence that technical divers who surface and demonstrate mild DCS symptoms may often get back into the water and breathe pure oxygen at a depth 20 feet/6 meters for a period of time to seek to alleviate the symptoms. This trend is noted in paragraph 3.6.5 of
DAN's 2008 accident report.
[18] The report also notes that whilst the reported incidents showed very little success, "[w]e must recognize that these calls were mostly because the attempted IWR failed. In case the IWR were successful, [the] diver would not have called to report the event. Thus we do not know how often IWR may have been used successfully."
I have seen that done first hand, with great success. In such a case, if it were not successful, the diver would have headed off to a chamber, and we would know about it. As that quote from DAN indicates, you really only find out about an IWR case when it doesn't work, and so the success rate is poor. Even if it doesn't work, you can't really be sure it didn't work. If someone shows up at a chamber and gets treatment for mild DCS after IWR, how are we to know how serious the case might have been had there been no IWR?