I still say to read your handbook regarding procedure. I'm sure by suspending you without telling you why is a breach of that, meaning the whole disciplinary will fall apart if you point that out to them.
Also, you should have said your account was hacked and you have no idea who by. Let them try and prove otherwise.
A stupid reason all the same though, what a bunch of babies! Reminds me of my disciplinary I posted earlier for a Facebook post.
You don't need to give reason for a suspension at the time of suspension, as long as it is quickly followed by an investigation meeting. A suspension is to protect both business and employee, not about discussing wrongdoing.