Legality of using photo from local event for promotion

I have a feeling I've read the answer to this at some point, but I can't seem to find anything addressing this particular situation at the moment, so maybe someone can help me out. Here's the situation:

Last year, I took some pictures of a dancer/singer at a local arts festival. It was a free event, and there were no restrictions on photography. I have a few of these pictures posted on my website. A few days ago, I was contacting by someone wanting to purchase a couple of these photos to use for their own event where they're having the same person performing. My question is, since these photos will be used for promotion of an event, would I need a release from the performer I photographed to sell the photos?

You wouldn't but they would. You can sell them the prints but if they plan on using them for commercial or promotional use they must acquire model releases which shouldn't be hard for them to get if they having the people come to the event. Or you can get the contact info of the people from the new event guy and get the releases yourself so you will have them for future use.

I actually sent them a release thinking this exact thing. I don't have the performer's contact information, so it wouldn't have been very easy for me to do it anyway. Plus, it's a very small event, so I don't think they're going to be willing to pay much. As such, I may have already scared them off, because I get the impression they figured I would give them the images for some nominal fee (or perhaps even nothing at all) for them to use in any manner they please. I usually just sell prints of my work, so I haven't done a good job in getting smart on this aspect. So even if this doesn't work out, this is certainly something I should know for the future.