Read it for the first time just now - it seems to me that Pierrot has stolen the narrator's purse (under the guise of dusting the chalk from their cloak) and successfully convinced them to blame Truth, instead. There's almost certainly more to it that I'm missing.
That's the core of it, but it's implied, not outright stated, and requires some tricky language parsing, basic theory of mind, and not being too distracted by the highly symbolic objects.