This has happened to me before. How long was the title of the save?
If
1. Blockland crashes shortly after you saved or
2. The save file's name was very long,
then that might cause a corruption. One of my saves, a while bacl, was something like:
Medieval Village RPG- with Ice Mountain.
then it came out in the folder as something like
Medieval Village RPG- wit#12%&639##71
So go to the actual save file, in the saves section, then whatever map it's on, and check that out.