Sorry to hear it.
I am always wary about leaving my garage doors open for this very reason. We live in a fairly isolated area, but my garage is pretty close to the street making a such a theft easy to accomplish. I won't even leave a mower or my snow blower out front for five minutes.
I learned my lesson after having my 1984 Johnson sailmaster 9.9 (one of the most popular sailboat auxialaries of all time) stolen off the back of my boat while it was on the mooring over 500 feet from the nearest shore. Locks? I had bought them, but not taken a moment to install any yet...after all...what can happen that far from shore?
That reminds me...I really should increase the security on my new boat. No outboard anymore luckily. I wonder if there is some way I can put a lock on my main? Oh well, somebody would probably just cut the sail and get it repaired.
Good luck catching the thief. Besides ebay I'd notify all the big used sail online sites. I'd also look contact everyone I could in the 361 owner's registry and warn them that they might be contacted to purchase the sail. I'd give that list to the police as well if there are any local owners. I doubt that anyone who owns a 361 would steal a sail if they can afford that boat, but you never know.
Good luck getting it back.