Android Core API .search() returns empty list

For some reason, the following code has stopped working as it used to. The .search() method now returns an empty list. This code has been working without any problems and alterations for months, serving hundreds of users. The file "myfile.txt" is always present inside the folder, but the .search() method cannot find it anymore. Is this due to API v1 Core API deprecation? It should continue to work until 6/28/2017. How can I solve this? Thank you!

List<Entry> searchforDatabaseResults = new ArrayList<Entry>(); 
searchforDatabaseResults = mApi.search("/", "myfile.txt", 0, false);
if (searchforDatabaseResults.size()!= 0) {
//...
}