If you're asking what my fix does, I'll try to explain from my understanding.
Blockland keeps an internal count ($pref::screenshotnumber) of how many screenshots you have taken. Every time you take one, Blockland just adds one to this count, then saves the picture as Blockland_####. It uses the internal count to determine where to save it, not the number of screenshots in your folder. Somehow, your count got jarred off significantly, possibly by a crash after a session where you took a large number of screenshots. Because of this, Blockland started saving them over your old screenshots. There is not a way to get the pictures it overwrote back, sorry.
The fix I offered above will set your count to 1232, the number of screenshots you said you have. That way, next time you ake a screenshot, it will increase the count, then save your picture to Blockland_1233.
