I don't think you can search directly by user but if you use the JSON API and dump out the detail of an event id, you can see the log entries which contain the name of the user that closed the event and work from there.

zenoss_api.sh evconsole_router EventsRouter detail '{"evid":"0050569b-02be-95f2-11e5-4f532c119e62"}'

Pretty-printed results:
'log' => [
[
'dpirmann',
'2015-08-31 11:29:27',
'state changed to Closed'
]
],

Additionally, I had a brief look thru the source code (/opt/zenoss/Products/Zuul/routers/zep.py) and there's a queryGenerator function but it doesn't appear "log" is one of the fields that can be directly queried.