How do I get my piano back from the ex?

I kept a portable piano at his place because I'd stay over often and was taking a piano class at college. Now we're broken up and he hasn't responded to my e-mails about returning it, but I know he's read them because he checks his mail as soon as he logs on the computer.

The piano cost over a hundred dollars and since I don't have a job it was a huge expense for me, I really need it back before classes start up again. What's the best way to get it back? It's only been a few days since I sent the first e-mail about it (sent two so far) and I'm worried it's too soon to call, text etc.