Here's what may have happened since her behavior is definitely not that of a hen with an obstruction in her oviduct. A yolk that enters the oviduct at ovulation can become lodged, not moving, remaining at the top of the oviduct and gathering layers of albumin (white). That was where she was when the vet saw her.
At some point in the last 24 hours, this hapless egg bounced out of the oviduct due to an oviduct malformation and spilled into the abdominal cavity, relieving her of the pain and discomfort she has been experiencing. This is what her perky behavior is telling us may have happened.
However, if this is what has happened, it has only bought her a little time before she faces the consequences of "internal laying". This is a condition where other ovum do the same thing, resulting in an accumulation of eggs in her abdominal cavity. At some point she will become very sick and death follows.
There is a very small chance this egg, if it isn't wrapped in too many layers of albumen, will absorb into her body, disappear in other words. We can't know, though, exactly what is actually happening, just the possibilities.
It's likely that your hen has a poorly developed oviduct to have all this happen. You should be prepared for all this to happen again, even though right now it appears she's over this crisis.
I suggest you return her to her normal routine with her flock as if none of this has happened and let her get back to normal life, as short as that prognosis may be.
