Here is my version just for amusement… Uses
Rhino.FileIO.File3dm.Read() to read all the 3dm files in a folder and access the layer table (without actually opening the files). If it finds one or more matches to a user-input layer name, it throws up a list box with all the matches. You can actually choose one of the files in the list and have it open in a new instance of Rhino (not sure how this works on Mac Rhino), or just Esc to close.
Right now it will also find files with layers that contain the input string but might not be an exact match (i.e if you type “Default” it will find that plus Default1, My Default, etc…). I can refine it to make exact matches work if need be.
FindFileWithLayerName.py (1.5 KB)