When attempting to find ungeocoded documents I'm getting a misleading error.

db.accounts.find({"locations.coordinates":{"$exists":false}})

returns this error;

"$err" : "geo field only has 1 element :: caused by :: $exists: false",
"code" : 13068

None of my coordinates have only one element.

db.accounts.find({"locations.coordinates":{"$exists":true}})

is successful.