My motorcycle was completely out of coolant, should i be concerned?

I recently bought a 2004 Honda VTX 1300. It only had 5000 miles on it, and i've put about another 500 on it in the last few months. I never checked the coolant level until today, and I noticed that the coolant reservoir looks completely empty. I haven't had any problems with the bike, it starts right up and runs great. And the temperature light has never turned on. The only thing i've noticed was today after i let the bike idle for about 15 minutes, i turned the engine off and heard a weird sort of whining sound, which stopped when i turned the power off. Anyways, i'm going to buy some coolant tomorrow, but i was wondering if i should be concerned at all that there reservoir was completely empty?
Added (1). I do plan on finding out if there's a coolant leak, and where. I guess my main question is whether it is possible that there's already permanent damage to the motor, even though it seems to run perfectly, and the temperature warning light has never lit up?

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