If anyone else encounters the same plug in the wild, please post the useful details that are (for reasons I don't understand) confidential.
What make and model is the EVSE? A photograph of the defective EVSE would also be useful. If I saw one like it, I wouldn't even bother getting out my calipers.
If this becomes a common problem (failure to release), perhaps modifying the LEAF charge port to have a less engaging lock tab would be the answer. Or a tool that is purpose-built to fit under the receptacle and force the lock tang up.
Remember that we are the curious, patient, and resourceful early-adopters. If this happened to my wife on a public charger, there would be some stressful phone calls, a useless AAA truck, and most likely wire cutters and vice grips employed. Such a plug wouldn't last a week in any public location -- it would be destroyed by someone less patient than clever.