Wow, we are so glad you enjoyed the game this much! This comment really made our day. Thank you for taking the time to write it.
Sorry about the bugs. We did our best to clean it up, but all of the code and the majority of bug testing was done by just one person (who was only just learning to code games, to boot). At some point we may do another update to address some of the issues, but not sure when we will get a chance to work on it. Will be a significant undertaking, as it has been a while.
As for the statues, yeah, some of them are pretty easy to miss. I don't know which ones you have already found, but I can give some general hints that may help. First, there is a spirit statue at (or very near) each of the four optional bosses; some of these require fighting and defeating the boss first, but not all of them. Second, there is a very obscure optional area/dungeon in the far north-western part of the world (the snow-covered region). The entrance is hidden. One of the spirit statues is there.
It has been so long since I worked on the game that I had to go back and check my notes and the game code to be sure. But there are in fact 17 of them!
Thank you again for playing, and for writing this very kind review. Cheers.