digitalv - 8:05 am on Sep 6, 2004 (gmt 0)

Pretend you've got someone else on the line and "mess up" when switching. Tell your forgotten caller to hang on, wait a few seconds, and then say "John, are you still there?"

If their name happens to be John they'll say yes. If it's not, they'll think you messed up and say "Nope, this is still ...". Then write the name down so you don't forget again, stupid :)