readOGR not reading in prj file?

Hi,

I'm currently using rgdal v 1.1-1 on R 3.2.2.  It appears my
projection file is not being read in by readOGR:

dFloodRisk <- readOGR(floodshapedir, shapebase)

OGR data source with driver: ESRI Shapefile
Source: "FloodShapes", layer: "2013Spring_Flood_Drawn"
with 8 features
It has 2 fields

proj4string(dFloodRisk)

[1] NA

I have to manually pass in the CRS:

dFloodRisk <- readOGR(floodshapedir, paste0(curYear, 'Spring_Flood_Drawn'), p4s='+init=EPSG:3857')

OGR data source with driver: ESRI Shapefile
Source: "FloodShapes", layer: "2013Spring_Flood_Drawn"
with 8 features
It has 2 fields

proj4string(dFloodRisk)

[1] "+init=EPSG:3857 +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0
+lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs"

Any thoughts on why readOGR doesn't automatically read in the prj
file?  Here's the content of the prj file:
PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Mercator_Auxiliary_Sphere"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",0.0],PARAMETER["Auxiliary_Sphere_Type",0.0],UNIT["Meter",1.0]]

Thanks so much for your help.

-- Vinh