Rehydrate the probe for a few days and try to calibrate it. I've done the same and had them work well. The calibration will tell you for certain; if it calibrates and holds calibration you may be OK. if it doesn't calibrate, or after calibration the reading don't hold in a known solution then the probe is bad and would need to be replaced.
When it happened to me I would spot check the probe for a few weeks before really trusting it; e.g., each weekend I would check the reading in calibration solution (or a solution with a known PH).
