You have got to wonder why they chose to only post their "thank you" messages on Facebook. It is like some of the NRHS chapters where you have to join a yahoo group to get information on their upcoming meetings. They did not use Facebook exclusively for promoting the event, why hide your thanks message in a site that requires membership. It seems like an opportunity missed.
But is is better than some of these organizations that never say "thank you" to their volunteers at all, then wonder why they cannot get volunteers for their future events. I have seen so much of that in railroad enthusiast organizations. One friend is program chairperson for an organization that invites guest speakers to their convention. They schedule them in competition with other events, including tours and their model train show. They never publish proper announcements of the programs, there is constant traffic and talking in the room, rude audience interference and comments, etc. They get people to volunteer just one time and then they usually tell the organization that they never want to do that again. Then he complains each year that he cannot get enough speakers for the convention. The real root of the problem is their officers think their organization is so important that the "honor" is them inviting the person to participate, and they can't understand it when people don't care to repeatedly endure their lack of planning and rudeness.
"We Repair No Locomotive Before Its Time"