Dennis -
Check the link and note the flows in CFS for the past week:
http://waterdata.usgs.gov/id/nwis/uv...cd=00065,00060
With stable flows at Heise Cable and on the Big Feeder for at least a week before your outing, no way could a spawner create a redd and deposit eggs where you found them.
Your guess that someone caught a brown and stripped her eggs is almost certainly right on the money.
John