Can't think of ANY reason why you haven't heard from the guy?
I can only think of 1 bad reason (he ripped you off)and TONS of good reasons...
Like maybe something bad happened to him...
A few years back I got massive blood clots in my lungs without warning (I was at work).
I spent a solid month in the hospital.
I don't own a cell phone or laptop,which I probably wouldn't have grabbed as they wheeled me into the ambulance...as I coughed up blood while trying to breath...
No computer/internet in the hospital (at least not then,I don't know about now).
Stuff happens to people all the time.
If he's a stand up guy you'll hear from him,if not I don't see $20.00 as something to get all upset about.
Change your biz practices,get payment ahead of time like everybody else,COD died a long time ago.