I think it was totally for the sake of fun.
I did something like this to the girl with the silver convertible in my apartment complex. I wrote "I think your cute -the green one" with "the green one" in green. I figured she'd get it, but the next day I saw her parked at the mailbox. I was new and was going to say hi, till she saw me and put her top and windows up
Now... if you keep getting notes... that's another ball of wax!