They make those nifty gadgets that enables you to find the remote control -- Sharper Image sells them -- but wait - you need to have the remote control first.
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Remote Control Finder
You could always try the gadget my parents used when I was a but a wee one, before the days of remote controls (I know that's hard to beleive) Have a kid or two and get them to be the remote control, you know they'll always come back when they're hungry or need money