arcpy - Using Search Cursor and Messaging Total Count of Items from Field in Layer that was Searched?

My program works but it is not displaying a message of the total sheet count found in attribute table that the search cursor searched through. For Example: It goes through the mxd chosen by user finds the layer with the name Grid in it and then is supposed to count the rows in the field Sheet_ID. End result is to print a message of the count found. My code is below:

import arcpy, os, sys
from os import path as p
from arcpy import mapping as m

mxdList = arcpy.GetParameterAsText(0).split(';')



sheet_count = ()

for mapDoc in mxdList:
    arcpy.AddMessage(mapDoc)
    mxd = arcpy.mapping.MapDocument(mapDoc)
    for lyr in m.ListLayers(mxd, "*, Grid"):
        if lyr.description == "*, Grid":
        max_list = []

        rows = arcpy.SearchCursor(lyr)
        for row in rows:
            max_list.append(row.Sheet_ID)
        sheet_count = max(max_list)
        arcpy.AddMessage('Sheet count: %s'%sheet_count)
        print 'Sheet count: %s'%sheet_count
    else:
        arcpy.AddError('No Layers in %s match data source'%mapDoc)