Some Fanpop members have previously tested this out, and their medals reappeared a few days after they rejoined that club. In some examples they even got a higher medal. I've seen it mentioned in other similar questions.
posted over a year ago
Unless you got your medal from adding screencaps, because they don't count anymore.
Aren't screencaps in older clubs still there, with the section just missing in clubs which were created since uploading screencaps was stopped? That's how it was last time I looked at the entire images section, anyway.
Screencaps are still here, they just don't count towards medals. I think there was like a year after the uploads were cut off that you could get a medal back that you'd earned for caps. Then... nada.