I think it's great you started a project, finished it and promoted it Mark. Most people don't make it that far.
As Others have said, I've been hearing about people making good with teespring. Mostly the guru's talking about how they killed it on facebook.
Though I did not know you needed a goal and a time frame to sell them. I understand why, but puts the pressure on, no?
Curious, what's the profit potential? It depends on the short and design I take it. Just wondering what could be made.
Like other have already mentioned, timing seems to be one big key. Remember hearing people doing well with sports teams at the right time.
I would guess one route would be to build up a facebook/fanpage following and then launching a shirt. Seems Pinterest could be a good place to sell, if you have followers.
Interesting topic.