There's plenty of evidence in this case, just possibly not enough to pass the threshold for a successful criminal prosecution. People get fired all the time for

There's plenty of evidence in this case, just possibly not enough to pass the threshold for a successful criminal prosecution. People get fired all the time for doing things that aren't illegal, and where there is strong but non-conclusive evidence of wrongdoing. For example, if I consistently take time off for being "sick", I'll eventually be fired, even though the company obviously won't be able to prove beyond a reasonable doubt that I wasn't sick on the relevant days.