Is there a logic fallacy for something could have happen so it did?

Is there a logic fallacy for something could have happen so it did?

Yes, appeal to possibility .

However, "John could have had apple pie so he did" is not an example of this fallacy. This is more of a statement of fact. If John had apple pie and the reason was "because he could" then so be it. That is what happened. However, if the fact that John ate the apple pie is in question, and the reason given is that it was possible that he ate it, therefore he must have, then this is fallacious.

The short phrase, "[J]ohn could have had apple pie so he did" is a statement, it does not pose a question. "He could have apple pie, but didn't" would be the same: no question presented. No conclusion drawn. No logical process involved.