Need Tech advice

Sitting in my hotel last night I had set the alarm on the Vette. Horn and lights. About two hours later the horn starts blowing. Not intermitent, and the lights were not blinking. Just a steady horn. No one was around the car at all.
Hit the FOB and it went off.
Reset the alarm and all was fine the rest of the night. Any ideas? Does she need a bath, a new battery or something?
Thanks

