There is a major construction done between Duisburg and Essen during the Autumn holidays of North Rhine-Westphalia. I was under the impression, the S1 is running a dertour ... but this is incorrect. Information available only in Germany language is here:
Verkehrsverbund Rhein-Ruhr - Totalsperrung Duisburg - Essen
You can go back to Derendorf and try to catch the S-Bahn S6.
The RE1 and RE6 should stop in Essen-Altenessen. There you have connection to the Essen local transportation network and can take the subway / underground to downtown Essen. This is better than "Schienenersatzverkehr" between Duisburg and Essen, especially during peak times.