I see this all too often. I open up iCal, double click to make a new entry. Maybe change the calendar it's on. Enter a title, enter a start time, click in aother field (like end time), then click elsewhere in the calendar to save the change. (since there's no SAVE button)
Then I watch the event, named properly, appear for an INSTANT and then disappear, only to be replaced by New Event, on the defaut time.
And I have to open the event and re-enter the name and time.
I've seen this happen over a dozen times, and it's irritating. 10.9.5, icloud syncing calendars, these events are on my My Computer calendars (not any of my imap calendars)
More than once I've missed it pulling that stunt, and missed an event because it just nuked it right after I entered it, and I didn't notice.
I work for the Department of Redundancy Department