Ask for model-specific storage guidance and consider the whole sink water system. The disposer, trap and connected hoses may retain water even when the sink looks empty from above.
What the observation tells you
Turning off the motor supply does not prepare plumbing for freezing conditions. Do not pour antifreeze, salt or another chemical into the disposer, and do not dismantle the mounting to drain it. Any property winterisation should account for all connected equipment and be planned appropriately.
A useful next step
Before returning the kitchen to use, check accessible areas for damage or leakage and follow the advised recommissioning procedure. Have uncertain connections assessed rather than testing them with a full sink.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.