We've been getting reports from Mac users about losing saves, so I'm stickying a solution post from one of our programmers, Oldbushie.
This only applies to the non-Steam version. Steam cloud helpfully backs up saves, so Steam version wouldn't run into this issue.
"This is a problem with Unity and Apple, not with our code. Unfortunately Unity places save files in a location that gets wiped on major Mac updates. This affects all Unity-made games, not just our own.
These are the two potential locations Unity saves to on the Mac:
/Users/<Username>/Library/Caches/<Company Name>/<Application Name>/
/Users/<Username>/Library/Application Support/<Company Name>/<Application Name>/
Supposedly, later versions of Unity save to the second location, but I haven't seen evidence of that yet. So if you don't want to lose save data from Unity games, back up the Unity-related folders in your Caches folder regularly.
In the meantime, email us at support (at) postudios (dot) com and we will be happy to provide you with a save that gets you close to where you were."
- originally posted on http://www.postudios.com/blog/forum/index.php?topic=14566.0