Ask HN: What to do when a developer goes dark?

Recently I wanted to upgrade a n old (but successful) project and put out a request I was looking for outside help without giving out project details. A good developer was interested and responsive. I was interested in his skillset so I sent him the project, all upgrades I was looking to do in great detail. I've tried to contact him several times since and I've not heard a peep from him. Should I be worried that he liked it and would lock me out for his own version or could it be a case of disinterest (which I would assume at least a courtesy reply of "not interested")?