What do you do when...

[The Holy Saint, Grand High Poobah, Master of Monkeys, Ehlers]

the problem is that I had THREE ideas. Two of them stayed till I got to work and could jot them down. The third I can't even remember anything about. I'll I remember is that when I had the third idea, I thought "that's THREE to remember," and then couldn't recall what number 2 was

[MsFish]

I used to get ideas at work alot, because I worked in retail, which is pretty brainless.  I used to write scenes and ideas on register tape in between customers when I was cashiering.  If I was in the stockroom or on break I'd write entire scenes on paper towels.  You can even do that while walking the floor, if you pace yourself.  I'm not sure if my manager ever noticed, but she knew I was a writer, so if she did notice she was probably amused.