maybe, maybe not. old water damage will sometimes bleed the color thru fresh paint. we had some wind damage to our roof that resulted in a water stain in teh hall ceiling. i primed/painted that area at least 4 tmies before it quit bleeding thru.

if the area grows bigger than the original stain, or is actually wet, then you still have a leak.

What was the water source of the original leak? rain?
Was it raining when the leak "reappeared"?

Caulking directly outside of where the stain was observed does not necessarily mean you've stopped anything. If the source was not positively identified you're shooting blind at stopping it.

just my 0.02

Thanks very much for this information. It is appreciated.

As stated before, the leak may or may not be repaired. With stains on plaster or sheetrock it needs to be primed with a stain killer primer or a flat poly to seal the stain. BIN alcohol based primer is one primer solution you could use.
Caulking is not a long term solution for repairing leaks around windows and doors. A correct flashing detail is.
Ron

gaila53, you said the owner caulked. I take it you rent?

You also said the owner plastered inside. It could just be the old stain bleeding through.

Watch it, if it keeps growing let your landlord know. He/She obviously cares about their property.

If it's the stain bleeding thru, a good fix is to use bleach on the stain. the bleach will eradicate the stain and most of the time it does not need to be re-painted.