I used the same one back in the spring and didn't have an issue but I could see it as an easy target to be hacked.
While some network the kiosk transaction uses "might" get hacked, there are usually an astronomical number of cards hijacked, so the activity is eventually noticed (but not before a lot of damage).
What most likely happened is that the thieves placed a scanner on the card reader at the kiosk for a period of time, then removed it. The scanners essentially fit onto the machine to look like part of the machine that should be there, or it's so slight and slim that it goes unnoticed. It copies your card when you insert it for the legal transaction. Card info stacks up in a memory chip until the bad guy retrieves it to collect the stolen data to be used for fraud.
Remote, rarely-tended kiosks such as one at a park gate are perfect targets for the thieves as they get ample opportunity to install and remove the device. It's long gone by the time any of the fraud shopping begins, so many cardholders never figure out how the theft occurred. The OP should complain to whoever operates that park - I'd bet 10:1 their machine had a piggyback scanner on it for a while, and they didn't do well at checking machine security.