I used your code and noticed that when creating the same event multiple times (translated to an incrementation of the count field in the event console), I get each time a different uuid... I think there is no direct correlation between the uuid you get and the evid. I also checked if it corresponded to the occurence uuids of the created event, but that wasn't the case...
Maybe the uuid you get is just identifying your call and not the event.
Can't be of much help here...
Good luck !