The original Nintendo DS came with two styluses, isn't that nice?
When I get a pen stylus (as soon as somebody makes one) I'll hopefully still have my old one as a backup.
They make them. I can't tell if you're just joking, but someone has one in my office and it's pretty neat. It's quite slim and has 2 springloaded pen tips, just pull a small tab to switch between pen and stylus. Doesn't fit in the N900 slot tho.
If only the stylus slot had a sensor to detect insert/removal, then we could have done something like notifying the user via LED or Vibra when the system goes to sleep.
I have found a useful workaraound for this is to file the fingernails on your dominant hand to a small point. These can be used instead of enabling the stylus at all, which will at least prevent you losing it. There is a question as to whether sharper fingernails should be installed by default on all n900 users. In this aspect, n900 is inferior to the iphone, which of course requires neither stylus nor nails. (But is useless in gloves)
Warning!!! Over sharpening your nails may cause serious bricking to your social life, nose interior or private parts (depending on what you do with your hand). Any user following this advice does so at your own risk.