The Elk Horn Club (two words) in Placerville was no where near a golf course. I think it is more likely that this was from the Elkhorn (one word) golf course in Stockton. The "rain checks are given out if you pay for a round of golf but get rained out - also sometime given out in the bar when some one buys you a drink and for whatever reason you can't drink it right then. Here is a link to the Elkhorn web site:

http://www.elkhorncc.com/

Here are a couple of "rain checks" from other golf clubs:
Del Paso Country Club in Sacramento

Sierra View Country Club in Roseville

And last a chip from the Elk Horn in Placerville