add Note

Usecases/README.md

@@ -54,6 +54,13 @@ This will run the simulation and save the output of `stdout` to a file named
 
 In order to create a new usecase, either modify one of the existing ones, or
 copy one of the existing cases into a new file and start working on your own.
+>>>
+**Note:**
+ It might happen, that not all usecases are running, due to forgetting to update
+the script. If that happens and you wanted to run that particular usecase,
+find a usecase that works and diff the two files, to see what's missing.
+>>>
+
 To understand how usecases are set up, let's have a look at the file
 `TP-R-2-patch-test.py` in
 [Two-Phase-Richards/two-patch/TP-R-two-patch-test-case/](./Two-Phase-Richards/two-patch/TP-R-two-patch-test-case/).