Is there luggage storage at the train station in Rudesheim, Germany?
According to Bahnhof.de there are no lockers at Rüdesheim (Rhein) station,
You might try looking on an app like Nannybag. There may be a hotel or restaurant that will hold your bags for a fee.
I usually go via Bingen, but if my memory is correct there's nothing much open at Rudesheim other than the platform and the ticket kiosk.
It doesn't look like Bingen Hbf has lockers, either.
You might find you can store your luggage at the TI office in Rüdesheim. It's about a half mile back up the river from the train station, near the KD dock.
Bingen does not have lockers, and most tourists don't want the main Bingen station either, as it's not in town, but it is closer to the walk on ferry (when that's running, which it doesn't all the time). Using the in-town stop puts you closer to the attractions and car ferry, which you can also walk on. No lockers there either.