I didn't see the video, but I suspect there is a temp where the light goes on, and you were at that temp...and then dropped below it enough that it went off...just like you thought.
Glad you're good, but keep a close eye on coolant level anyway.
I'm so depressed. No one wants to come see me in NYC: Sat, Oct. 8, 6 p.m. at Greenwich Village Comedy Club.
Mangofy your E46!