MP3 player not able to play music (and not showing up in Finder or iTunes)
I believe that a voice recorder would be seen by Mac OS X as either an MP3 player or a flash drive. In that case, one of the last articles published by Apple on support for non-Apple music players in iTunes is here. It is not a recent list, but I have very little reason to believe that any other players are being added to it. In fact, it would seem reasonable that Apple has stopped support for most MP3 players other than iPods at this time. 

The best bet for any non-Apple MP3 player drivers for Mac OS X would be to go directly to the website of PoGo. After running a few searches, I could not even find their website (pogo.com actually takes you to an Electronic Arts gaming site). 

I am sorry to say that there may not be a way to access your device. I would think that Mac OS X would at least try and mount it as a USB flash drive, but since it didn't I am not sure what other options are out there for you. 

Have you tried using that same USB cable and PoGo device on a Windows machine? At the very least, if Windows can mount it that would tell you that both the device and cable are okay. Windows does reasonably well with its generic drivers for things like cameras and flash drives. 

For illustration's sake, let's say that Windows is the only way to have access to your device. If so, then a way to get to use your Mac with it would be with something like Parallels, VMware or Boot Camp. You could have Windows load the files and those files would be accessible to you from the Mac's Finder. You could then drag the files into iTunes. But it just feels like too much effort installing all of that. But then again, the PoGo might be a great voice recorder. Hope this helps and good luck.