There is certainly a history endpoint in the API for device events but for whatever reason, which may well include it not being intended for end user use yet, it hasn’t been documented for the end users. The basic format is:
https://api.smartthings.com/v1/history/devices?locationId={{locationId}}&deviceId={{deviceId}}
There are several other parameters that limit what is returned but I don’t really know the format (although you can see it in the returned paging URLs).